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Madrid, Noise by the river: Bird or cricket?

Madrid, Noise by the river: Bird or cricket?


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I currently live in Madrid, Spain. In July there was a loud animal near the river, in an out of town area surrounded by grassland, with trees along the river.

It's continued into August, though it has reduced.

It sounds like a cricket in general tone and rhythm, but it is always high in the trees, and sounds too deep to be an insect. It's in the frequency range of a squawking bird, so if it's a cricket it must be huge.

On the other hand, if it was a bird, I should have been able to spot one.

Does anyone have any idea what it is?

The sound is rhythmic, rasping note, with two beats of equal duration but slighly different tone, repeated over and over again without any pause. The animal that makes it calls continuously for long periods.

EDIT: thanks to AliceD for the comment, I didn't realise we had cicadas in Europe. It could be a cicada, but it's deeper and more consistent / regular in its song than this one:

https://www.youtube.com/watch?v=DSdxm52VwOg


In this case i am going to agree with AliceD, because I live in Greece and here we hear cicadas everywhere. But in Madrid, there is a other kind of cicada that its "song" is more noisy and more deep.In this video you can hear how your cicada sings.https://youtu.be/mah26og11ms


As suggested by AliceD, it does indeed appear to be some kind of cicada. I went down the river and heard one calling, unusually far from the river (30m) where there are lower, newly planted trees. I was able to approach it and take this photo which unfortunately isn't very good.

It's possible that it's even the same species as the video I added to the question. It may be that the cicada in the video did not sing with a regular pattern because it was disturbed by the observers. My cicada refused to sing at all while I was watching him, preferring not to draw attention to himself. I took 3 photos before he began to walk up the tree. On my fourth photo he became startled, flew off, and immediately resumed singing elsewhere.

The cicada in the video sounds more tinny than the ones by my river. That may be an audio effect.


The originally posted song and video suggest a cicada in the genus Cicada (the type genus of the family Cicadidae, which is known from southern Europe, eastern Asia, and north Africa); some identified recordings of this genus can be found at this page on European cicadas. So far I can only find references to C. orni and C. barbara in Spain, but the recordings of those species given on the European cicadas site don't exactly match, although the physical appearance does suggest C. orni (keeping in mind that the white waxiness often gets rubbed off adult cicadas over time). Since the orni recording on the website is from Slovenia, it may just be that the cadence of the song in that location differs from that of Spain (or in different temperatures, or in different courtship contexts). There are a few other Youtube videos described as orni from Spain with similar sounds (e.g., https://www.youtube.com/watch?v=3Z4STY71C-8). I don't know if there are other candidates besides orni and barbara in Spain.


Noise pollution from gas compressors changes abundance of insects, spiders

IMAGE: Many arthropod families, including wolf spiders, dropped in numbers in response to compressor noise. The decrease in wolf spiders could be due to their reliance on subtle vibrations to. view more

Credit: Florida Museum of Natural History photo by Lary Reeves

GAINESVILLE, Fla. --- The relentless roar of natural gas compressors influences the numbers of insects and spiders nearby, triggering decreases in many types of arthropods sensitive to sounds and vibrations, a collaborative Florida Museum of Natural History study shows.

Populations of grasshoppers, froghoppers, velvet ants, wolf spiders and cave, camel and spider crickets dropped significantly in areas near gas compressors, while leafhopper numbers rose.

These shifts in arthropod communities could set off a cascade of larger-scale ecological consequences, as insects and spiders play fundamental roles in food webs, pollination, decomposition and overall ecological health, said study co-author Akito Kawahara, assistant professor and curator at the museum's McGuire Center for Lepidoptera and Biodiversity at the University of Florida.

"Noise pollution affects all kinds of animals, and insects are no exception," Kawahara said. "They might be small, but they're the dominant animals on the planet in terms of numbers. What happens to them affects whole ecosystems."

The study joins a growing body of research on how artificial noise alters animal behavior and disrupts ecosystems and is the first to examine noise pollution's effects on arthropod distribution and community diversity.

Gas compressors, which can range from minivan- to warehouse-sized, extract and move natural gas along a pipeline, emitting intense, low-frequency noise. Previous studies have shown noise pollution from compressors changes the activity levels and distribution of bats and birds, key predators of insects and spiders.

Kawahara joined a multi-institutional research group, led by the study's first author Jessie Bunkley and principal investigator Jesse Barber of Boise State University, to test how the landscape-scale noise produced by gas compressors affects arthropod communities, many of which rely on sound and vibrations to find food, meet a mate, communicate and detect predators.

The research team used pitfall traps to take a census of spider and non-flying insect populations at San Juan Basin, New Mexico, the second largest natural gas field in the U.S. The team tested five sites with compressors and five ecologically-similar sites without compressors and compared the relative abundance of specimens.

Compressor sites had 95 percent fewer cave, camel and spider crickets, 52 percent fewer froghoppers and 24 percent fewer grasshoppers than sites without compressors. For every 10-decibel increase in noise, velvet ant populations dropped 56 percent and wolf spiders decreased by 44 percent. Unexpectedly, leafhopper numbers surged in response to noise, increasing 44 percent for each additional 10 decibels of sound.

Some arthropods, such as jumping spiders, ground spiders, ants and leaf beetles, showed no significant differences in their numbers between sites.

All arthropod groups that responded to louder background sound levels or compressor noise make or sense sounds or vibrations, suggesting compressor noise could directly interfere with or mask important information they receive or exchange.

Compressor noise could negatively affect wolf spiders, for example, because they are hunters that depend on vibrations to detect prey. Conversely, noise could act as a "predator shield" for leafhoppers, hiding their sounds and movements from their natural enemies.

But parsing out why a particular group of arthropods increased or decreased in response to compressor noise is difficult, Kawahara said. While the number of crickets in the Rhaphidophoridae family plunged in response to compressor noise, crickets in the Gryllidae family did not seem to be affected.

"The range of changes in arthropod abundance sheds light on the fact that we're dealing with a very complicated network of animal interactions," Kawahara said.

He pointed to the value of museum collections as archives of past biodiversity that can record changes to the environment over time.

"We are rapidly changing our environment in terms of sound, light, air and climate," he said. "Unless we have historical documentation of what was in an area at a particular time, it's hard to detect these changes at a fine scale. Museum specimens document biodiversity over hundreds of years, offering those snapshots of time."

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.


Transcript

[MUSIC CLIP WITH CICADAS AND CLARINET]

CURWOOD: David Rothenberg is a philosopher and musician who likes to collaborate when he plays his clarinet, as here, in this track from his latest CD - Cicada Dream band - which features birds, bugs and whales. Now, biologists tell us that creatures sing or call or howl for a reason &ndash to mark their territory, to warn of danger or to attract potential mates. But David Rothenberg, who is a professor at the New Jersey Institute of Technology, thinks that some animals sing simply for the joy of it, and that&rsquos why he likes to play along with them. Professor Rothenberg joins us now from Cold Springs, New York. Welcome to Living on Earth.

ROTHENBERG: Thanks so much for inviting me.

CURWOOD: So growing up what was your personal interaction with nature and its sounds?


Rothenberg played with a Veery thrush and also manipulated the sound by slowing it down. (Photo: Christopher Elliot Flickr CC BY 2.0)

ROTHENBERG: Well, I grew up in Connecticut, kind of in the suburban countryside, and I was always going outside behind my house into the meadow and by the river and listening to sounds. I was always interested in music and also natural world, and trying to figure out how to connect them.

CURWOOD: So, David, everyone hears the sounds of nature walking through the woods, but not everyone hears music like you do. One example is a little experiment you did with a Veery Thrush song. Let's play the thrush song as you would hear it in the forest.

[VEERY THRUSH SONG AT NORMAL SPEED]

CURWOOD: And then you took that song and slowed it way down.

[VEERY THRUSH SONG AT SLOW SPEED]

CURWOOD: Wow! Who would've known? What did you take away from this little experiment?

ROTHENBERG: I mean, this is one of the most surprising examples of taking a birdsong in its real speed and slowing it down, kind of into the human realm of hearing. And you hear what's already in there, and you hear what the birds are getting. And you kind of grasp how this song can mean so much to the female Veerys that hear it. You know, birds hear five times faster than we do. The Veery on its own is going [WHORLY SOUNDS], and this is kind of a somewhat familiar but strange sound you hear in the woods. To bring it into the human realm, bring the pitch down, this song is an amazing example of the music contained in that little phrase, it really sounds like a jazz trumpet phrase.


David Rothenberg plays his clarinet with a Starling. (Photo: Courtesy Cheetah Television Ltd)

[VEERY THRUSH SONG AT SLOWED DOWN]

ROTHENBERG: [SINGS JAZZ TUNE SIMILAR TO SLOWED VEERY SONG] It's got all the qualities of a good jazz phrase. It's got not only a form and structure, but a real quality of performance and emotion and verve to it somehow like, if you were playing that it in a lesson with your teacher, they'd say, "Yeah, you got it. You&rsquove got it figured out."

CURWOOD: Uh-huh. You know, I always thought John Coltrane got his rifts from the Wood Thrush.

ROTHENBERG: Ah! What did he say to that? He probably did.

CURWOOD: [LAUGHS] Now you have a new record out it's called the "Cicada Dream Band." And there are sounds from cicadas, crickets, whales, but you also have some other musicians on this.

CURWOOD: How does playing with creatures change when you're joined by other human musicians?


Cicada Dream Band&rsquos album cover. (Photo: Charles Lindsay)

ROTHENBERG: Well, this album came out of the concerts we did when the cicadas were emerging last year, 2013, in the New York metropolitan area, and every 17 years this happens. I had heard that 17 years before, that Pauline Oliveros, the famous experimental composer had done a whole festival of cicadas so I said, "Let's do it again." So we performed in New York City and in some other places, and in the record we ended up with Pauline playing this kind of digital accordion called a V-accordion along with Timothy Hill, who&rsquos an overtone singer. He specializes in singing&mdashyou can sing more than one note at the same time, kind like birds and insects can do. And so we formed this group, and so we kind of based the music, you know, not so didactically like some of my other records have done, but really kind of use it as part of the mix. So we are playing live. I was playing clarinets and also computer, playing some of these sounds, and we were kind of improvising together to form music around the whole possibility that all these sounds are out there in the natural world. And what I hope in this whole process is that my own music and the music of my collaborators&mdashhuman and from other species&mdashhas changed by the encounter, like it leads to something new that we couldn't do on own.

CURWOOD: You've played with different kinds of creatures: birds, whales, cicadas even. So talk about the similarities and differences of playing with those different animals.

ROTHENBERG: Well, the thing is with playing with insects then you are one sound in the midst of millions. It's very humbling to make a little noise in around you. You hear so many individuals altogether forming this kind of collective musical composition where everyone's doing their own little part and somehow it fits together. And although at first it might sound like noise when you pay closer attention to it you realize there's a lot of organization going on there. With birds you get a sense you're connecting to an individual: an individual is doing something and you're responding to it. And of course it's one thing to take the song, slow it down, make it sound that you interact with, like in the studio or in a concert where you&rsquore playing the recording. That's kind of easy in a way. What's more challenging and kind of daring and surprising is to do it in the wild where you don't know what's going to happen. Like last year I was out in Berlin in late spring playing with nightingales in these parks. Berlin is somehow full of nightingales and they just sing very intensely in the middle of the night.


Rothenberg plays music with many creatures including the Nightingale. (Noel Reynolds Flickr CC BY 2.0)

CURWOOD: So how did the nightingales respond to your clarinet?

ROTHENBERG: They kind of keep jamming with you. Scientists have told us there's three ways the nightingale will respond to a sound played to it.

ROTHENBERG: They will alternate. They will let you do your sound then they'll do something.

[NIGHTINGALE SINGING AND ALTERNATING CLARINET]

ROTHENBERG: Or they can try and compete with you and jam what you're doing. When alternating, it's a more peaceful sense of, OK, you've got your space I've got mine. When they're kind of interrupting you constantly it's more like a competitive situation: they're trying to define their territories against yours.

[NIGHTINGALE SINGING AND COMPETING WITH CLARINET]


Comparison of the frequency and duration of a nightingale&rsquos song to that of a humpback whale. (Photo: David Rothenberg)

ROTHENBERG: And then finally, the most superior, top nightingales just ignore what you do&mdashmaybe they sing, maybe they don't. They couldn't care less.

[NIGHTINGALE SINGING AND IGNORING CLARINET SONG]

ROTHENBERG: This is similar to, say, human jazz musicians&mdashthese three types of musicians you will easily meet onstage. Any jazz musician would confirm that.

CURWOOD: [LAUGHS] Well, maybe the jammers are trying to teach you how to play the clarinet a little better.

ROTHENBERG: I'd say sometimes. You know, there's a recent scientific study written by these scientists in Berlin saying that, you know, the nightingales are either playing rhythmic clicks or whistle songs [CLICKING AND WHISTLING], but occasionally they make this sound, which the scientists describe as an "ugly" sound like [MEAH MEAH]. But I listened to it, and all the other musicians we had out there playing with nightingales&mdashit just sounded like a cool bent blue note like a [MEAH MEAH]. And whenever it did it, everyone would smile and laugh because it sounded so cool. It was interesting: the scientists just thought it was unmusical, and all the musicians said it was very musical.


David Rothenberg, headphones on, listens to the sounds of humpback whales and plays along into a microphone. His sound is then transmitted to the whales through an underwater speaker. (Photo: Dan Sythe/Courtesy David Rothenberg)

CURWOOD: So birds like half notes, huh?

ROTHENBERG: They like blue notes like in between the major and minor, like we all do, these in between things that you can't quite define, just like the Veery song has this swinging bluesy quality: ba-da ba-da ba-da. That is surprising ending, but it's just the perfect ending. And every animal that sings is really a world in itself. They all have their own aesthetic sense, something Charles Darwin talked about. Like he wrote in "Descent of Man", birds have a natural aesthetic sense. They appreciate beauty that's why they've evolved beautiful feathers and beautiful songs. People often forget that. It's not a very common subject to study biology&mdashthe aesthetics of evolution&mdashbut I'm happy to say more and more scientists are starting to take this more seriously.

CURWOOD: A long time ago, Beatrice Harrison went out with her cello to play with nightingales. What did you think of her music?

ROTHENBERG: Well, what&rsquos so fascinating about that story is this is the first outdoor radio broadcast ever made so it was a really big deal for the BBC to do this in the 1920s. And they repeated it every year up until World War II it was a very famous and popular program. And she was confirming just what I was saying: that you can play any sound, the nightingales will join in.

CURWOOD: Let's listen to a little bit of Beatrice Harrison.

[BEATRICE HARRISON CELLO PLAYING DVORAK&rsquoS &ldquoSONGS MY MOTHER TAUGHT ME&rdquo WITH NIGHTINGALE OBBLIGATO]

ROTHENBERG: To listen to this, you really have to put yourself back in mood of the 1920s, when a sound just like that, just as scratchy, was heard as being incredibly realistic, incredibly unique, something utterly new, like a sound recording outdoors mixing humanity and nature. No one had heard anything like that before hearing this. So you just have to say, wow, listen to this humans can reach across to nature playing a human instrument that birds respond [to] and more than that, this broadcast on shortwave was heard all over the world.

CURWOOD: David, what do you learn about nature, or at least the creature you play with when you do this?


Diagram of David Rothenberg&rsquos setup when he plays with whales underwater. (Photo: David Rothenberg and Martin Pedanik)

ROTHENBERG: You learn that there is music in nature it's not just a human imposition. It's this aspect of evolution that Charles Darwin was well aware of, but today it's hard to find a biology textbook that admits that evolution creates a lot of weird, cool, beautiful stuff. I wrote a book called "Survival of the Beautiful" just dealing with this aspect of evolution: that evolution produces all this beauty, which is amazing, but you can't always explain it away with some practical purpose. And I think this has profound implications for how we understand nature. The way so many animals communicate is in a way much more like music than like language. They repeat the same phrases over and over and over again, so they're not just saying some specific message like, "Hey, I'm here. I'm hungry. Look at me." They need to say this with the phrases that are shaped and formed, and you find that in all kinds of animal sounds, even in these long songs of humpback whales, the complete song of which takes about 20 minutes to sing. Already in the 1970s, Katie Paine was writing that these songs have a structure, and you could say they have a sense of rhyme at the end of a long phrase. They come to the same sound. And they'll sing something different, and it'll come to the same ending &ndash a sound like [SCREECH] at the end of a long phrase.

CURWOOD: OK, you listen to the animals, and you play along. So to what extent do they listen?

ROTHENBERG: Well, that's a good question. We can study the hearing apparatus of different animals so we know what kinds of frequencies they hear, but it's harder to know what's going on in their minds. Birds have been the most studied in this regard. You can tell what goes on inside the brain of a songbird. Certain areas light up when certain sounds are played or sung. They do respond to certain kinds of things. What's so fascinating with insects is that many of them make sounds they can't even hear. Why does that happen?

CURWOOD: And the answer is?

ROTHENBERG: We don't know. Much of this is just not known. The notion that animals are making music has been understood by humans for thousands of years. Musicians have thought about it. Scientists have thought about it, but they debate whether it's a useful way to think about nature in a scientific way. Is it just a human subjective imposition or is it a useful way to analyze that?

CURWOOD: Let&rsquos listen to another clip now. This is from your record Whale Music. The tune is called "Never Satisfied".


Humpback whale glides by. (Photo: Courtesy Tomawak Productions)

[WHALE SOUNDS WITH CLARINET]

CURWOOD: What was it like playing with the whales? Where were you? When was it? How long did it go on?

ROTHENBERG: It's not so easy to play clarinet along with humpback whales. One reason is that they're underwater and I was sitting on a boat wearing headphones. You can't tell where the sound is underwater there's no sense of space. It's just everywhere around. It's ether louder, nearer or quieter, further. So this whale was right under the boat. You could almost hear him without the headphones at all. And what's interesting about humpback whales is they&rsquore always changing their song, always listening for new sounds, and it makes it interesting to play with them because sometimes, only sometimes, they respond to what I'm doing. I have to say I have done this for many hours, and most of the whales seem to ignore me, no surprise. But in this one example I showed you, you can really hear that as the clarinet plays a steady note [MIMICKS CLARINET NOTE], then the whale actually tries to go [WHALE MIMICKS NOTE]. He tries to sing in a more steady way than he usually does.


A Humpback whale breaches. (Photo: Courtesy Tomawak Productions)

ROTHENBERG: Whales don't usually sing horizontal steady sounds. They're usually more going [UP NOTE] or [DOWN NOTE], they go up and down like that. And so this is a kind of surprising moment where the whale showed some interest. And so, at that moment, you feel like, ah, maybe something's going on here&mdashmaybe there's a sense of getting through to another species through music.

CURWOOD: David Rothenberg is a musician, author and professor of Music and Philosophy at the New Jersey Institute of Technology. Thanks so much, Professor, for taking this time.


The insect that hears like a human, with ears on its knees

Every time you put on some music or listen to a speaker’s words, you are party to a miracle of biology – the ability to hear. Sounds are just waves of pressure, cascading through sparse molecules of air. Your ears can not only detect these oscillations, but decode them to reveal a Bach sonata, a laughing friend, or a honking car.

This happens in three steps. First: capture. The sound waves pass through the bits of your ear you can actually see, and vibrate a membrane, stretched taut across your ear canal. This is the tympanum, or more evocatively, the eardrum. On the other side, the eardrum connects to three tiny well-named bones—the hammer, anvil and stirrup—which link the air-filled outer ear with the fluid-filled inner ear.

The bones perform the second-step: convert and amplify. They transmit all the pressure from the relatively wide eardrum into the much tinier tip of the stirrup, transforming large but faint air-borne vibrations into small but strong fluid-borne ones.

These vibrations enter the inner ear, which looks like a French whisk poking out of a snail shell. Ignore the whisk for now – the shell is the cochlea, a rolled-up tube that’s filled with fluid and lined with sensitive hair cells. These perform the third step: frequency analysis. Each cell responds to different frequencies, and are neatly aligned so that the low-frequency ones are at one end of the tube and the high-frequency ones at another. They’re like a reverse piano keyboard that senses rather than plays. The signals from these cells are passed to the auditory nerve and decoded in the brain. And voila – we hear something.

All mammal ears work in the same way: capture sound convert and amplify and analyse frequencies. But good adaptation are rarely wasted on just one part of the tree of life. Different branches often evolve similar solutions to life’s problems. And that’s why, in the rainforests of South America, a katydid—a relative of crickets—hears using the same three-step method that we use, but with ears that are found on its knees.

Grasshoppers, crickets and locusts all have knee-ears that, at just a fraction of a millimetre long, are among the tiniest ears in the animal kingdom. Even though countless numbers of these insects had been dissected, no one had really understood the structures of these ears.

Fernando Montealegre-Z from the University of Bristol has filled in the rest of the gaps. Fresh from recreating the sound of a Jurassic cricket, he turned to studying a katydid called Copiphora gorgonensis, a green insect with an orange face, topped with a unicorn-like spike and comical beady eyes.

He analysed the legs of living katydids using a CT scanner designed for tiny objects. The scans revealed a pair of eardrums (or tympanal membranes) on each knee. That much we already knew about. But Montealagre-Z also discovered two new organs.

The first– the acoustic vesicle (AV)—is like an uncoiled version of our cochlea, a tapering hollow fluid-filled tube. Other scientists had assumed that the AV was a simple blood vessel, but Montealegre-Z knew that couldn’t be right. For a start, it’s only found in the first pair of legs where the katydid’s ears are. It contains a line of sensitive cells called the crista acustica, like the hair cells that line our cochlea. Their role is the same – to analyse frequencies.

The AV is connected to each eardrum by a completely new structure called the tympanal plate (TP). It looks like just another part of the insect’s hard outer cuticle, but using lasers, Montealegre-Z found that it vibrates in time with the eardrum. This plate is the katydid’s version of our three ear bones – a stiff lever that converts the air-filled outer ear with the fluid-filled auditory vesicle. And just as our eardrums have 17 times more surface area than our stirrups, the katydid’s eardrum has 13 times more surface area than its tympanal plate. The effect is the same: large faint vibrations are converted into small strong ones.

So here’s how a katydid hears. Step one: the two eardrums captures sound, just as ours do. Step two: the tympanal plate sends these vibrations into the fluid-filled auditory vesicle, amplifying them in the process. Step three: the waves travel down the crista acustica, whose cells respond to the various frequencies and send that information to the insect’s nervous system. It’s the same set-up as in our own ears, but in structures that are a hundred times smaller.

Despite the similarities, there are obvious differences between the katydid’s ears and our own, besides the location, and the paired eardrums. Our cochleas hold between 17,000 and 24,000 hair cells, while the katydids only have 14 to 70. Those cells cover a range of frequencies between 10 and 50 kiloHertz. That spans around three very high-pitched octaves, and it’s much broader than the only sounds that katydids make to each other – a courtship note of around 18 to 23 kHz. Montealagre-Z thinks that the insects have evolved to hear other sounds beyond their own serenades – perhaps they high-frequency calls of hunting bats.


Madrid, Noise by the river: Bird or cricket? - Biology

I love the sound of crickets in the evening. They always remind me of summers where I grew up in North Carolina. It seems like we had more crickets there, and where my grandparents lived in the mid-west, than we do here in western Oregon (or should I say HEAR in western Oregon?). I don't know if that's true, but it seems like that to me.

L ate last summer I had a tree cricket in my yard, happily chirping his little tune every night. I was glad to have him move in because I've never heard a cricket right here in my yard, which is in a fairly urban area. I sat on the patio many evenings over several weeks listening to his song, which was eventually joined by another.

S o I was excited when I heard chirping again yesterday afternoon, but I thought it was a little early in the day for a tree cricket to be singing. I went in search of the chirping's source, which was pretty high up in a Cascara tree, and found. a cicada?!

Cicada (probably Okanagana rimosa) in a Cascara tree
I 've seen cicadas by the thousands when visiting my grandparents in Illinois and Missouri, but they were bigger and greener. And I've never seen or heard one in Oregon.

Cicada (probably Okanagana rimosa) in a Cascara tree
H aving spent my fair share of time outdoors in Western and Central Oregon, I probably would have said we don't have cicadas here. That's why I grabbed my camera as fast as I could, and snapped these pictures. They're not great because it was about 10 feet up the tree, and this was the only angle I could get.

A fter I got the photos I sat down to do a little research, to see if there really were cicadas in Oregon, or if this was just a wayward traveler blown in by some freak wind. I was somewhat surprised to read that there really are cicadas in Oregon.

A local biologist, named Max, wrote on his blog (Apartment Biology) that the cicadas found in Oregon "are smaller, emerge in lower densities, and are not as loud as the ones found in the southern and eastern parts of the country." He reported hearing many cicadas - most likely of the genus Okanagana - at Shute Park in Hillsboro. He also found their exuvia (shed exoskelotons) on the trunks of the conifers in the park.

I looked around for my visitor's exoskeleton, but didn't find anything. I think he must have flown into my yard. And soon enough after I took the photos, he flew away - probably in search of a better cicada social scene.

W hile researching cicadas in Oregon, I ran across a great site called Cicada Mania. Everything you've ever wanted to know about cicadas, plus lots of photos, videos and even sound clips of different cicada songs. After tweeting a photo of my cicada to their Twitter account (@cicadamania), I learned that we have 32 species of cicadas in Oregon, all belonging to the Okanagana, Platypedia, or Neoplatypedia genus. Judging from the limited view of my cicada, they thought it was probably Okanagana rimosa, sometimes called Say's Cicada.

H ere are some interesting cicada facts, from Wikipedia:

  • Cicadas are insects in the order Hemiptera.
  • About 2,500 species of cicada have been described, and many remain to be described.
  • Cicadas are related to leafhoppers and spittlebugs, but NOT locusts.
  • Cicadas do not bite or sting in a true sense, but may mistake a person's arm or other part of their body for a tree or plant limb and attempt to feed (only if allowed to rest on a person's body for an extended amount of time.)
  • Many people around the world regularly eat cicadas.
  • Cicadas have three small eyes, or ocelli, located on the top of the head between the two large eyes.
  • The male cicada has loud noisemakers called "tymbals", their song is not created by structures rubbing together, as in crickets.
  • Some cicadas produce sounds up to 120 dB- loud enough to cause permanent hearing loss in humans should the cicada sing just outside the listener's ear.
  • Cicadas live underground as nymphs for most of their lives, emerging in the final nymphal instar, and molting one last time to become adults.
  • After mating, the female cuts slits into the bark of a twig, and into these she deposits her eggs. When the eggs hatch, the newly hatched nymphs drop to the ground, where they burrow.
  • Most cicadas go through a life cycle that lasts from two to five years. Some species have much longer life cycles.

S o how about it - has anyone else seen cicadas in Portland or other parts of Oregon?


Quelea quelea (weaver bird)

The red-billed quelea is a small weaver bird native to sub-Saharan Africa and renowned for its attacks on small-grain crops within Africa. It is the most numerous bird species in the world, with peak post-breeding population estimated at 1,500,0.

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Pictures

TitleAdult male
CaptionQuelea quelea lathamii (weaver bird, red-billed quelea) adult male, in breeding plumage. Botswana. February, 2008.
Copyright©Robert. A. Cheke-2008
TitleAdult female
CaptionQuelea quelea lathamii (weaver bird, red-billed quelea) adult female. Botswana. February, 2008.
Copyright©Robert. A. Cheke-2008
TitlePair
CaptionQuelea quelea lathamii (weaver bird, red-billed quelea) a pair, in breeding plumage. Botswana. February, 2008.
Copyright©Robert. A. Cheke-2008
TitleAdult male
CaptionQuelea quelea aethiopica (weaver bird, red-billed quelea) adult male, in breeding plumage. Tanzania. March, 2008.
Copyright©Robert. A. Cheke-2008
TitleNest
CaptionQuelea quelea lathamii (weaver bird, red-billed quelea) nest. Botswana. January, 2008.
Copyright©Robert. A. Cheke-2008
TitleEggs in nest
CaptionQuelea quelea lathamii (weaver bird, red-billed quelea) eggs in nest. Botswana. February, 2008.
Copyright©Robert. A. Cheke-2008
TitleChicks in nest
CaptionQuelea quelea lathamii (weaver bird, red-billed quelea) chicks in nest. Botswana. February, 2008.
Copyright©Robert. A. Cheke-2008
TitleFlock coming to drink
CaptionQuelea quelea (weaver bird, red-billed quelea) flock coming to drink at a pool. Botswana. March, 2005.
Copyright©Robert. A. Cheke-2008

Identity

Preferred Scientific Name

Preferred Common Name

International Common Names

  • English: red-billed quelea
  • Spanish: quelea comun
  • French: travailleur a bec rouge

Local Common Names

EPPO code

Summary of Invasiveness

The red-billed quelea is a small weaver bird native to sub-Saharan Africa and renowned for its attacks on small-grain crops within Africa. It is the most numerous bird species in the world, with peak post-breeding population estimated at 1,500,000,000. The red-billed quelea is mainly granivorous, except when feeding its chicks insects or when eating insects prior to migration or breeding, and it relies on a supply of grass seeds to survive. When unable to find grass seeds or when opportunities arise, quelea will attack crops. It is a major pest throughout much of sub-Saharan Africa and can cause significant economical losses.

The bird is inherently nomadic, following rain fronts, and this nomadism accounts for its invasions into areas where it was previously absent.

Taxonomic Tree

  • Domain: Eukaryota
  • Kingdom: Metazoa
  • Phylum: Chordata
  • Subphylum: Vertebrata
  • Class: Aves
  • Order: Passeriformes
  • Family: Ploceidae
  • Genus: Quelea
  • Species: Quelea quelea

Notes on Taxonomy and Nomenclature

The red-billed quelea was originally described by Linnaeus in 1758 as Emberiza quelea, with type locality erroneously given as India. In 1760 Brisson painted a specimen of the red-billed quelea, probably from Senegal, and in 1766 Linnaeus corrected the type locality to Africa, which was later restricted to Senegal by Sclater. The generic name Quelea was first used by Reichenbach in 1850.

There are three recognized subspecies: the nominate West African form Q. quelea quelea ( Linnaeus, 1758 ), which occurs from Senegal to Chad and the Central African Republic the east African subspecies Q. quelea aethiopica ( Sundevall, 1850 ), found from Sudan to Somalia, eastern Democratic Republic of Congo to Kenya, Tanzania and northeast Zambia and the southern African subspecies Q. quelea lathamii ( Smith, 1836 ), which occurs in Angola, southern Democratic Republic of Congo, Malawi and from Mozambique to South Africa. A fourth subspecies Q. quelea spoliator Clancy 1960 is now treated as synonymous with Q. quelea lathamii ( Jones et al., 2002 ) and the form known as Q. queleaintermedia is considered to be included within the nominate.

Hybridisation with red-headed quelea Q. erythrops is only known in captivity (Craig, 2010).

Description

The following descriptions are adapted from Craig (2004, 2010):

Red-billed quelea are small, short-tailed, sexually dimorphic weaver birds about 12 cm long and weighing 15 to 26 g. The sexes differ in appearance according to season. In their breeding plumage males are polymorphic, with different amounts of black, yellow, pink, purplish or white in the head and neck region and different amounts of colouration on the belly (Ward, 1966). The colour patterns of the males’ plumage are not signals of quality (Dale, 2000) but are thought to be involved in individual recognition processes (Dale et al., 2001). However, the redness of the males’ bills is an indicator of condition and quality (Dale, 2000) and social dominance (Shawcross and Slater, 1984). Males of the nominate race typically have a black face ‘mask’, consisting of a black forehead, lores, cheeks and upper throat surrounded by varying amounts of pink, yellow, purple or black. Sometimes the mask is white. The surrounding colour may end on the lower throat or stretch as far as the belly, with the remainder of the underparts being light brown or white with some dark striations. The upperparts are light brown with dark longitudinal stripes, particularly centrally, with those on the rump paler. Tail and upper wing dark brown flight feathers edged greenish yellow. Eye has narrow red orbital ring and brown iris. Legs orange. Bill bright red. The non-breeding plumage of males lacks any bright colour, with much of mask, forehead and crown becoming grey-brown with dark streaks, chin, throat and faint supercilium white bill becomes pink and legs flesh-coloured. Females in breeding plumage resemble non-breeding males but have yellow bill and eye-ring. Non-breeding female has a pinkish bill.

Eggs are laid in clutches of 1-5, usually 3, measure 18 x 13 mm and are bluish or greenish, occasionally with some dark spots. Clutches of 6 have been noted but these may be the result of egg-dumping by females that are not the nest-owners. Nestlings are born naked with wisps of down on shoulders and crown, with white bills. Eyes open and feathers appear on day 4.

Within 2-3 months of hatching, juvenile birds complete a post-juvenile moult to resemble non-breeding adults, but with grey head, whitish cheeks and buff edges to flight feathers and wing coverts, followed 1-2 months later by a pre-nuptial contour moult, when they begin to assume the adult breeding plumages. Nestlings have a lavender-tinged horn-coloured bill that turns orangey purple before the post-juvenile moult, then pinkish-purple and finally red ( Jones et al., 2002 ).

The different subspecies are primarily distinguished by the colours of the adult male breeding plumages. Adult breeding Q. quelea quelea have a buff crown, nape and underparts and a broad band on the forehead. Adult breeding males of Q. quelea aethiopica generally lack the black band across the forehead and the buff wash on their underparts, which may be replaced with a pink wash. Adult breeding males of Q. quelea lathamii have a broad band on the forehead and mainly white underparts. However, there is much variation and some individuals cannot be ascribed to a subspecies based on morphology alone. Some interbreeding between subspecies may occur at transition zones.

Distribution

The red-billed quelea is found in sub-Saharan Africa. Its known distribution was described by Magor and Ward (1972). Grid squares in which the southern African subspecies Q. quelea lathamii has been recorded have been mapped by Mundy and Herremans (1997) and Cheke et al. (2007, Fig. 1) and the known breeding sites of this subspecies were mapped by Cheke et al. (2007, Fig. 3).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Africa

History of Introduction and Spread

The only suspected case of red-billed quelea having been introduced is the self-perpetuating population on Réunion. The birds have been present since 2001, but how they reached the island is unknown, although the cage-bird trade is suspected. Quelea have recently invaded the Western Cape of South Africa (Oschadleus, 2009) and bred there (Anonymous, 2013).

Introductions

Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Réunion <2001 Yes Safford (2013) Probably pet trade. Firmly established on west coast between St-Paul and St-Pierre, where probably increasing.

Risk of Introduction

Red-billed quelea can only survive in semi-arid areas and already occur throughout most such habitats in Africa, but there are a few remaining places on the African continent to which they could be introduced.

If strict quarantine measures or restrictions on cage-bird imports are circumvented then the red-billed quelea could be introduced to islands other than Réunion, or even to suitably dry habitats on other continents, perhaps in South or Central America.

Habitat

Avoids forest, including miombo woodland. The red-billed quelea is principally found in semi-arid areas of dry thornbush grassland such as the Sahel. It is also present in farmland, where it attacks crops. As it needs to drink every day, the red-billed quelea is always within about 30km of water. It is occasionally found in wet habitats and may congregate in huge flocks at edges of water-bodies, such as Lake Ngami, Botswana, when the lake floods. It requires bushes, reeds or trees in which to nest or roost. The red-billed quelea can be found up to 3000m above sea level but usually only occurs up to 1500m.

Habitat List

CategorySub-CategoryHabitatPresenceStatus
Terrestrial ManagedCultivated / agricultural land Principal habitat Harmful (pest or invasive)
Terrestrial ManagedCultivated / agricultural land Principal habitat Natural
Terrestrial ManagedManaged grasslands (grazing systems) Secondary/tolerated habitat Natural
Terrestrial ManagedDisturbed areas Secondary/tolerated habitat Natural
Terrestrial Natural / Semi-naturalNatural grasslands Principal habitat Natural
Terrestrial Natural / Semi-naturalRiverbanks Principal habitat Natural
Terrestrial Natural / Semi-naturalWetlands Principal habitat Natural
Terrestrial Natural / Semi-naturalScrub / shrublands Principal habitat Natural
Terrestrial Natural / Semi-naturalArid regions Principal habitat Natural

Hosts/Species Affected

Quelea have been recorded eating the following crops: barley (Hordeum vulgare), buckwheat (Phagopyrum esculentum), bulrush or pearl millet (Pennisetum glaucum), finger millet (Eleusine coracana), foxtail or italian millet (= manna Setaria italica), common or proso millet (Panicum miliaceum), oats (Avena), rice (Oryza sativa), sorghum (Sorghum bicolor and S. caffrorum), teff (Eragrostis tef), triticale (Triticum x Setale) and wheat (Triticum durum). Quelea do not attack maize on the plant as their bills are too small to cope with the large seeds, but they will eat crushed maize at feedlots. At the start of wet seasons, early maturing crops are in danger from adult birds on their early rains migrations and, later on in wet seasons, crops are particularly vulnerable to roaming flocks of juvenile birds that have recently left the nest. In dry seasons, irrigated crops are threatened by birds of all ages.

Host Plants and Other Plants Affected

Biology and Ecology

Extra-pair fertilizations sometimes occur with quelea, with 31% of offspring being unrelated to at least one behavioural parent (Dallimer and Jones, 2007). All of the southern African populations of Q. quelea lathamii are a single inter-breeding population (Dallimer et al., 2003). Despite this lack of population structure, there is some sub-structure, with evidence for male-biased dispersal ( Dallimer et al., 2002 ). The male colour patterns are inherited but the mask and breast colours are independently assorted (Dale, 2000). Genes coding for quelea carotenoid colours have been investigated by Walsh et al. (2012).

Reproductive Biology

The red-billed quelea is a communal breeder, building nests in colonies that are usually found in thorn trees such as Acacia tortilis, A. mellifera and Dicrostachys cinerea, but occasionally in reeds or sugar cane, or other plants listed by Jarvis and Vernon (1989) . Some of these colonies are massive, stretching to up to 20 km in length and 1 km wide and involving millions of birds (such as at Malilangwe, Zimbabwe), with nests at densities of 30,000 nests per hectare. More than 6000 nests have been counted in one tree (Craig, 2010).

Nests are built over a 2-3 day period and only by males. The nests of Q. quelea lathamii are oval balls of interwoven grass, 20-130 mm tall, 100 mm wide and 89-06 mm deep. The nests are unlined. The entrance hole is 39-58 mm wide and 24-28 mm high with an overhanging porch of 22-26 mm (Jarvis and Vernon, 1989b). Males display at their nests to attract females. The clutch size varies from 1-5, usually 3, and is determined by the reserve protein levels of the females (Jones and Ward, 1976). Clutches of 6 have been noted but these may be the result of egg-dumping by females that are not the nest-owners. Colonies are synchronized and incubation takes 10-12 days. Nestlings are born naked with wisps of down on shoulders and crown, with white bills. Eyes open and feathers appear on day 4. Both parents feed the nestlings during a fledging period of 10-11 days and for a few days after they leave the nest.

Physiology and Phenology

Before migration, quelea build up their fat reserves by feeding on insects such as termites, with the amount of fat laid down linearly related to the distance to be travelled (Ward and Jones, 1977). Before breeding, protein-rich food such as termites and green grass seed is eaten, and reserve protein levels – the amount of labile stores in muscle sarcoplasm (Kendall et al., 1973) – reach a peak before declining, as they are used up by the efforts involved in reproduction (Jones and Ward, 1976).

The red colouration of the eye-ring, legs and bill of breeding males is carotenoid-based. The red in bills and feathers relies on the presence of enzymatically derived keto-carotenoids (Dale, 2000).

Wild birds tend to live for 2-3 years (Bird Trader, 2013), although they can live longer. A captive bird lived for 18 years and 9 months (Butler, 1913).

Activity Patterns

Quelea are thought to exchange information on locations of food sources when gathered at roosts or colonies (Ward and Zahavi, 1973). Huge flocks of breeding birds leave colonies and roosts in undulating streams at or just before dawn, apparently in directions of food or water sources, making a distinct noise due to numerous wing-beats. Small flocks return to roosts via a drinking site from 30 minutes before dusk, with numbers of arriving birds increasing as dusk approaches, sometimes in attenuated streams. Stragglers may continue to arrive up to 15 minutes after dusk. The roosting birds move about within the roost and are noisy for a further 30 minutes or so before they settle down. Behaviour at roosts and preferred vegetation for roosting were described by La Grange (1989).

After breeding, adults and juveniles form partially separated flocks, with most juveniles remaining in the natal area after parents have moved on. It is these flocks of juveniles that are responsible for most crop damage. In non-breeding season, birds roost communally in huge flocks, often at sites used in successive years. They also form ‘day roosts’ at the hottest time of day, when they congregate in vegetation near food or water.

Flocks feed on the ground in rolling motions, with trailing birds constantly leap-frogging leaders to exploit the next source of fallen seeds, behaviour which minimizes foraging in areas that have already been exploited. They also take seeds directly from plants.

Red-billed quelea drink daily and flocks will appear at water-holes, usually perching on surrounding vegetation before going down to the water.

Population Size and Structure

The red-billed quelea is considered to be the most abundant terrestrial bird on earth, with a peak post-breeding population estimated at 1,500,000,000 (Craig, 2010), and as many as 170,000,000 in southern Africa alone (Yeld, 1993). The population in Kruger National Park, South Africa, was estimated to be 33,000,000 (Craig, 2010).

The populations of Q. quelea lathamii in southern Africa comprise one inter-breeding population (Dallimer et al., 2003) and this is probably also true of Q. quelea quelea in West Africa and Q. quelea aethiopica in eastern Africa.

Quelea mainly eat grass and cereal seeds from the plant and from the ground, preferring grains 1 x 2 mm in size. For crops eaten, see Hosts/Species Affected.

When red-billed quelea need to build up protein, such as before migrations or breeding, quelea will feed on insects including Orthoptera, Hymenoptera, Coleoptera, Hemiptera, Dermaptera, Lepidoptera, Isoptera and Diptera, as well as spiders and snails. Up to half of the diet fed to nestlings consists of insects. Breeding females eat snail shells and calcareous grit, seemingly to enhance calcium levels for egg production (Jones, 1976).

A colony of more than 12,000 nests per hectare was estimated to have a monthly consumption of 1845 kg of seeds per hectare and 214 kg per hectare of insects (Craig, 2010).

Associations

When in small groups, quelea often associate with weavers Ploceus spp. and bishops such as the red bishop Euplectesorix, and in West Africa they may join flocks with the golden sparrow Passer luteus and various species of estrildids (Craig, 2004). Sometimes red-billed quelea form mixed roosts with weavers, estrildids and the barn swallow Hirundo rustica.

Environmental Requirements

The red-billed quelea is found in semi-arid vegetation in Africa, from sea level to 3000m, usually with thorn bushes and not far (up to about 30km) from water. It is frequently found on agricultural land. It usually nests and roosts in thorn bushes, but a variety of other plants may be used for communal gatherings including sugar-cane, reeds and eucalypts.

Natural Food Sources

Food SourceFood Source DatasheetLife StageContribution to Total Food Intake (%)Details
Amaranthus
Brachiaria
Cenchrus
Chloris
Commelina
Dactyloctenium aegyptium
Digitaria milanjiana
Digitaria velutina
Echinochloa colonum
Echinochloa pyramidalis
Egragrostis papposa
Eleusine indica
Eriochloa macclounii
Eriochloa meyeriana
Hyparrhenia anthistirioides
Indigofera
Ischaemum brachyantherum
Oryza barthii
Panicum laevigatum
Megathyrsus maximus
Paspalum commersonii
Paspalum orbiculare
Paspalum urvillei
Pennisetum ramosum
Pennisetum typhoides
Portulaca
Schoenfeldia gracilis
Setaria acromelaena
Setaria chevallieri
Setaria flabellate
Setaria nigrirostris
Setaria pallidifusca
Setaria purpureo-sericeum
Setaria spacelata
Setaria verticillata
Sorghum almum
Sorghum verticilliflorum
Sporolobus
Tetrapogon cenchriformis
Tetrapogon tenellus
Themeda triandra
Urochloa mosambicensis
Urochloa trichopus

Climate

ClimateStatusDescriptionRemark
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation/25])
BS - Steppe climate Preferred > 430mm and < 860mm annual precipitation

Natural enemies

Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Acanthoplus discoidalis Predator Juveniles not specific Cheke et al. (2003)
Cheloctonus jonesii Predator Juveniles not specific Vincent and Breitman (2010)
Crocodylus niloticus Predator Adults not specific Ash et al. (2009) Craig (2004) N/A
Dendroaspis polylepis Predator Juveniles not specific
Haemoproteus Parasite Adults/Juveniles not specific Durrant et al. (2007) Sychra et al. (2010) N/A
Pelomedusidae Predator Adults not specific Craig (2010) N/A
Plasmodium Parasite Adults/Juveniles not specific Durrant et al. (2007) Sychra et al. (2010)

Notes on Natural Enemies

Eighty-one species were listed by Thiollay (1989) as natural enemies, comprising birds, monkeys, galagos, squirrels, mongooses, foxes, jackals, hyaenas, cats, genets, civets, ratels, warthogs, lions and leopards, and there are numerous other publications reporting avian predation of quelea, such as Jarvis and Vernon (1989) , Bernitz (2010) and Buij (2012). Most records refer to the predation of fledglings and adults, but some predators, including snakes, take eggs and nestlings. The Nile crocodile Crocodylus niloticus was seen attacking drinking quelea in Zambia (Craig, 2004) and one individual reported by Ash and Atkins (2009) in Ethiopia used its tail to force birds from vegetation on riverside banks into the water, where it would then eat them. The diederik cuckoo Chrysococcyx caprius is thought to be a brood parasite (Craig, 2010). Invertebrate predators include the armoured bush cricket Acanthoplus discoidalis Walker (Cheke et al., 2003) and the scorpion Cheloctonus jonesii Pocock (Vincent and Breitman, 2010).

Means of Movement and Dispersal

Natural Dispersal

All three subspecies move in association with the rains. In West Africa the movements of Q. quelea quelea are generally south-north and then north-south, but the opposite strategy may also be adopted (Manikowski et al., 1989). For instance, Ward (1965 1971) proposed that in Nigeria birds travel 300-600km southwards during their early-rains migration, at the start of the rains in June-July, when the rain causes their grass-seed food to germinate. Thus, they reach areas such as the Benoue River valley, where the encroaching rains have already caused grasses to set seed. Then, after six weeks, the birds set off northwards until they find a suitable breeding habitat, breed, and then repeat the process in progessive moves further north, as ‘itinerant breeders’. Others have pointed out that some populations travel northwards at the start of the rains to exploit remaining ungerminated seeds (Manikowski et al., 1989). The situation in Senegal and Gambia also differs but remains to be understood, although southeastwards moves followed by northwestward return movements seem likely.

In eastern Africa, the movements of Q. quelea aethiopica are more complicated, especially where there are bimodal rain patterns which may allow individual birds to breed up to four times in a year. It is thought that there are two sub-populations. The ‘intermedia’ group move from Tanzania in the early rains migrations to southern Somalia, from where they return to breed in central Tanzania in February-March, followed by itinerant breeding migrations to successively more northern sites, usually culminating in central Kenya in May. Meanwhile, the ‘aethiopica’ group moves from its dry season areas in its early rains migrations from northern and central parts of Sudan and Ethiopia in May-June, to then breed in the south of these countries and in South Sudan, returning north during August-October ( Jaeger et al., 1989 ).

Although the southern African subspecies Q. quelea lathamii is not differentiated genetically (Dallimer et al., 2003), it has been shown to have a migratory divide (Dallimer and Jones, 2002 Dallimer et al., 2003). Birds in dry season quarters in Zimbabwe in October-November will move in their early rains migrations, either south towards South Africa or Mozambique or west-north-west towards Angola. Those reaching southern South Africa and Mozambique will have flown over the rains to where conditions will soon permit breeding, which will be followed by breeding migrations progressively further northeast. Those reaching Angola will perform similar movements in the opposite directions. Additional populations that spent the dry season in either southern South Africa or Angola will have been forced by the first rains to travel northwestwards or southeastwards, respectively, in September-October. That this description conforms with the birds’ known activities was confirmed by observation of breeding in areas predicted by a forecasting model based on the above scheme (Cheke et al., 2007).

Ringing studies have confirmed movement patterns from South Africa. The longest distance between ringing and recovery sites is 2545 km, for a bird ringed in South Africa and recovered in the Democratic Republic of the Congo (Oschadleus, 2000).

After fledging successfully, most juvenile birds are deserted by their parents, which move on generally in separate flocks, in which there is some evidence of sexual segregation and male-biased dispersal away from the natal group ( Dallimer et al., 2002 ). There is also evidence that some birds return to the same dry season quarters in successive years (Borello and Cheke, 2011).

Intentional Introduction

The population in Réunion was probably due to intentional introduction.


Contents

The name "crayfish" comes from the Old French word escrevisse (Modern French écrevisse). [2] [3] The word has been modified to "crayfish" by association with "fish" (folk etymology). [2] The largely American variant "crawfish" is similarly derived. [2]

Some kinds of crayfish are known locally as lobsters, [4] crawdads, [5] mudbugs, [5] and yabbies. In the Eastern United States, "crayfish" is more common in the north, while "crawdad" is heard more in central and southwestern regions, and "crawfish" farther south, although considerable overlaps exist. [6]

The study of crayfish is called astacology. [7]

The body of a decapod crustacean, such as a crab, lobster, or prawn (shrimp), is made up of twenty body segments grouped into two main body parts, the cephalothorax and the abdomen. Each segment may possess one pair of appendages, although in various groups, these may be reduced or missing. On average, crayfish grow to 17.5 cm (6.9 in) in length. Walking legs have a small claw at the end. [8]

Four extant families of crayfish are described, three in the Northern Hemisphere and one in the Southern Hemisphere. The Southern Hemisphere (Gondwana-distributed) family Parastacidae, with 14 extant genera and two extinct genera, live(d) in South America, Madagascar, and Australasia. They are distinguished by the absence of the first pair of pleopods. [9] Of the other three Northern Hemisphere families, the three genera of the Astacidae live in western Eurasia and western North America, while the 15 genera of the family Cambaridae and the single genus of Cambaroididae live in eastern Asia, eastern North America, and Mexico. [10]

North America Edit

The greatest diversity of crayfish species is found in southeastern North America, with over 330 species in nine genera, all in the family Cambaridae. A further genus of astacid crayfish is found in the Pacific Northwest and the headwaters of some rivers east of the Continental Divide. Many crayfish are also found in lowland areas where the water is abundant in calcium, and oxygen rises from underground springs. [11]

In 1983, Louisiana designated the crayfish, or crawfish as they are commonly called, as its official state crustacean. [12] Louisiana produces 100 million pounds of crawfish per year with the red swamp and white river crawfish being the main species harvested. [13] Crawfish are a part of Cajun culture dating back hundreds of years. [14] A variety of cottage industries have developed as a result of commercialized crawfish iconology. Their products include crawfish attached to wooden plaques, T-shirts with crawfish logos, and crawfish pendants, earrings, and necklaces made of gold or silver. [15]

Australia Edit

Australia has over 100 species in a dozen genera. It is home to the world's three largest freshwater crayfish:

  • the Tasmanian giant freshwater crayfishAstacopsis gouldi, which can achieve a mass over 5 kg (11 lb) and is found in rivers of northern Tasmania[16]
  • the Murray crayfishEuastacus armatus, which can reach 2.5 kg (5.5 lb), although reports of animals up to 3 kg (6.6 lb) have been made. It is found in much of the southern Murray-Darling basin. [17]
  • the marron from Western Australia (now believed to be two species, Cherax tenuimanus and C. cainii) which may reach 2.2 kg (4.9 lb)

Many of the better-known Australian crayfish are of the genus Cherax, and include the common yabby (C. destructor), western yabby (C. preissii), and red-claw crayfish (C. quadricarinatus). [18]

The marron species C. tenuimanus is critically endangered, while other large Australasian crayfish are threatened or endangered.

New Zealand Edit

In New Zealand, two species of Paranephrops are endemic, and are known by the Māori name kōura. [19]

Other animals Edit

In Australia, New Zealand, and South Africa, [20] the term "crayfish" or "cray" generally refers to a saltwater spiny lobster, of the genus Jasus that is indigenous to much of southern Oceania, [21] while the freshwater species are usually called yabbies or kōura, from the indigenous Australian and Māori names for the animal, respectively, or by other names specific to each species. Exceptions include western rock lobster (of the Palinuridae family) found on the west coast of Australia the Tasmanian giant freshwater crayfish (from the Parastacidae family) found only in Tasmania and the Murray crayfish found along Australia's Murray River. [ citation needed ]

In Singapore, the term crayfish typically refers to Thenus orientalis, a seawater crustacean from the slipper lobster family. [22] [23] [24] True crayfish are not native to Singapore, but are commonly found as pets, or as an invasive species (Cherax quadricarinatus) in the many water catchment areas, and are alternatively known as freshwater lobsters. [25]

Fossil records of crayfish older than 30 million years are rare, but fossilised burrows have been found from strata as old as the late Palaeozoic or early Mesozoic. [26] [27] The oldest records of the Parastacidae are in Australia, and are 115 million years old. [28]

Crayfish are susceptible to infections such as crayfish plague and to environmental stressors including acidification. In Europe, they are particularly threatened by crayfish plague, which is caused by the North American water mold Aphanomyces astaci. This water mold was transmitted to Europe when North American species of crayfish were introduced. [29] Species of the genus Astacus are particularly susceptible to infection, allowing the plague-coevolved signal crayfish (native to western North America) to invade parts of Europe. [30]

Acid rain can cause problems for crayfish across the world. In whole-ecosystem experiments simulating acid rain at the Experimental Lakes Area in Ontario, Canada, crayfish populations crashed – probably because their exoskeletons are weaker in acidified environments. [31]

In several countries, particularly in Europe, native species of crayfish are under threat by imported variants, particularly signal crayfish (Pacifastacus leniusculus) [32] [33]

Food Edit

Crayfish are eaten worldwide. Like other edible crustaceans, only a small portion of the body of a crayfish is eaten. In most prepared dishes, such as soups, bisques and étouffées, only the tail portion is served. At crawfish boils or other meals where the entire body of the crayfish is presented, other portions, such as the claw meat, may be eaten. [ citation needed ]

Global crayfish production is centered in Asia, primarily China. In 2018, Asian production accounted for 95% of the world's crawfish supply. [34]

In the United States, crayfish production is strongly centered in Louisiana, with 93% of crayfish farms located in the state as of 2018. [35] In 1987, Louisiana produced 90% of the crayfish harvested in the world, 70% of which were consumed locally. [36] In 2007, the Louisiana crayfish harvest was about 54,800 tons, almost all of it from aquaculture. [37] About 70–80% of crayfish produced in Louisiana are Procambarus clarkii (red swamp crawfish), with the remaining 20–30% being Procambarus zonangulus (white river crawfish). [38] Optimum dietary nutritional requirement of freshwater crayfish, or crayfish nutrient specifications are now available for aquaculture feed producers [39]

Like all crustaceans, crayfish are not kosher because they are aquatic animals that do not have both fins and scales. [40] They are therefore not eaten by observant Jews. [41]

Bait Edit

Crayfish are preyed upon by a variety of ray-finned fishes, [42] and are commonly used as bait, either live or with only the tail meat. They are a popular bait for catching catfish, [43] largemouth bass, smallmouth bass, striped bass, [44] perch, pike [45] and muskie. When using live crayfish as bait, anglers prefer to hook them between the eyes, piercing through their hard, pointed beak which causes them no harm therefore, they remain more active. [46]

When using crayfish as bait, it is important to fish in the same environment where they were caught. An Illinois State University report that focused on studies conducted on the Fox River and Des Plaines River watershed stated that rusty crayfish, initially caught as bait in a different environment, were dumped into the water and "outcompeted the native clearwater crayfish." [47] Other studies confirmed that transporting crayfish to different environments has led to various ecological problems, including the elimination of native species. [48] Transporting crayfish as live bait has also contributed to the spread of zebra mussels in various waterways throughout Europe and North America, as they are known to attach themselves to exoskeleton of crayfishes. [49] [50] [51]

Pets Edit

Crayfish are kept as pets in freshwater aquariums. They prefer foods like shrimp pellets or various vegetables, but will also eat tropical fish food, regular fish food, algae wafers, and small fish that can be captured with their claws. A report by the National Park Service [52] as well as video and anecdotal reports by aquarium owners [53] indicate that crayfish will eat their molted exoskeleton "to recover the calcium and phosphates contained in it." [52] As omnivores, crayfish will eat almost anything therefore, they may explore the edibility of aquarium plants in a fish tank. However, most species of dwarf crayfish, such as Cambarellus patzcuarensis, will not destructively dig or eat live aquarium plants. [54]

In some nations, such as the United Kingdom, United States, Australia, and New Zealand, imported alien crayfish are a danger to local rivers. The three species commonly imported to Europe from the Americas are Orconectes limosus, Pacifastacus leniusculus and Procambarus clarkii. [29] Crayfish may spread into different bodies of water because specimens captured for pets in one river are often released into a different catchment. There is a potential for ecological damage when crayfish are introduced into non-native bodies of water: e.g., crayfish plague in Europe, or the introduction of the common yabby (Cherax destructor) into drainages east of the Great Dividing Range in Australia. [55]

Sentinel species Edit

The Protivin brewery in the Czech Republic uses crayfish outfitted with sensors to detect any changes in their bodies or pulse activity in order to monitor the purity of the water used in their product. The creatures are kept in a fish tank that is fed with the same local natural source water used in their brewing. If three or more of the crayfish have changes to their pulses, employees know there is a change in the water and examine the parameters. [56]

Scientists also monitor crayfish in the wild in natural bodies of water to study the levels of pollutants there. [56] [57] [58]


MATERIALS AND METHODS

Animals and housing

Seven male greater mouse-eared bats (Myotis myotis) were used for experimentation. The animals were captured as juveniles in August 2005 near Freiburg, Germany, for the present investigations under licence from the responsible authority (Regierungspräsidium Freiburg, licence#55-8852.44/1095). Bats were held and tested in specially designed facilities at the University of Tübingen, Tübingen, Germany (approved by Regierungspräsidium Tübingen). They were housed in a flight cage of 2 m×1.5 m×2 m (length×width×height) with an inverted light regime [8 h:16 h (darkness:light)]. The bats received food (mealworms– larvae of Tenebrio molitor Linnaeus 1758), and water ad libitum during the experiments. Their diet was also supplemented with desert locusts (Schistocerca gregaria Forskal 1775) once a week and with vitamins and minerals once every four weeks. All seven bats were in good health at the end of the experiments and remained in the Tübingen animal unit thereafter for further investigations of how traffic noise impacts on bat foraging ecology.

Flight room and setup

Bats were tested in a large flight room with dimensions of 13 m×6 m×2 m (length×width×height) walls and ceiling were covered with sound-absorbing foam to reduce echoes and reverberations. Two equally sized compartments [2.5 m×3 m×2 m(length×width×height)] were constructed by erecting a dividing wall made from PVC and sound-absorbing foam(Fig. 1). Each compartment was equipped with six cylindrical landing platforms (diameter, 40 cm height, 10 cm). The platforms were arranged in two rows of three, 20 cm apart. Mealworms,as food reward, could be offered on a plastic Petri dish inserted on the centre of the platforms.

A loudspeaker (Swans, RT2H_A Arcadia, CA, USA) was mounted on the wall at a height of approximately 1.8 m at the rear end of each compartment for the playback of background noise. The speakers were tilted slightly downwards and directed towards the platform array in an attempt to broadcast sound as homogenously as possible. Test measurements showed maximal variations of 3 dB in the incident sound pressure levels [SPL (measured 80 cm above the platforms)].

Schematic representation of the flight room and the experimental setup (not to scale). Each of the two foraging compartments was equipped with a loudspeaker and six landing platforms, two of which contained live mealworms. The room and the division between the compartments were lined with sound-absorbing acoustic foam. A video camera and infrared illumination served to document the bats' behaviour.

Schematic representation of the flight room and the experimental setup (not to scale). Each of the two foraging compartments was equipped with a loudspeaker and six landing platforms, two of which contained live mealworms. The room and the division between the compartments were lined with sound-absorbing acoustic foam. A video camera and infrared illumination served to document the bats' behaviour.

Experimental procedure

In each trial, one compartment was the `stimulus compartment' where sound was played back and the other compartment was the `silent compartment' where the loudspeaker was activated but an empty file was played. Sound played back in the stimulus compartment was also audible in the silent compartment. Due to the dividing wall, it was attenuated by 17 dB in comparison with the stimulus compartment (measured at the two platform fields SdB02 sound level meter,01dB-Stell, MVI technologies group Villeurbanne, France). We used four different stimulus types of playback: (1) silence – the loud speaker was activated and an empty file was played back. The silence treatment was a control and served to measure the baseline of the bats' search effort allocation in the two compartments (2) broadband, digitally generated noise,which served as a broadband control (3) traffic noise recorded 7.5 m from a highway [30.7±2.5 passing vehicles min –1 (mean±s.d.)] and (4) noise recorded from strongly moving reed vegetation (reed bed running alongside a river, which flows across M. myotis foraging habitats bats are known to hunt on meadows adjacent to these reeds B.M.S., personal observation).

The experiments were divided into three periods of eight days. Different stimuli were used for each period. Each of the four stimuli was presented once on the left side and once on the right side for each bat, resulting in eight experimental conditions per period (i.e. one a day). To factor out day or sequence effects, each bat received a different experimental condition on a given test day (Latin square design). Two out of the six platforms per compartment were continuously baited with 4 g of mealworms, which corresponded to approximately 40 individual larvae. The mealworms produced faint rustling noises with main energy between 3 and 20 kHz, with stronger clicks of up to 50 kHz and above. Measured at 10 cm distance, the loudest peaks ranged from approximately 45 to 62 dB SPL. The mealworm rustling was thus roughly similar to the sounds produced by a carabid beetle (typical greater mouse-eared bat prey) walking on soil, meadow or moist leaf-litter(Goerlitz et al., 2008). Rewards were not placed on the same platform location (front, middle, back)within the two compartments to achieve a homogeneous distribution of the rewarded dishes within the sound field of the speakers. As a result, there were 12 different combinations to choose from. For a balanced design, we used each combination twice within the 24 experimental days, avoiding repeating a dish combination within any of the 8 day periods. The two rewarded dishes of each side were always unrewarded dishes the following day to avoid place conditioning. The assignment of rewarded dishes was independent between the two sides to deter the bats from extracting information from the rewarding scheme of the stimulus compartment from the silent compartment. Platform positions were exchanged between consecutive experiments in order to avoid olfactory labelling on the currently rewarded platforms (scent left from bats of previous session of the day).

Data acquisition started after a 15 day training phase without noise playback in which the bats were accustomed to the flight room. The bats learned to search for prey in the two compartments without much training effort. Bats were tested individually during their natural activity period. After 15 capture events (brief landing on a baited platform, followed by in-flight smacking sounds, which indicate that the bat was chewing food) at a given platform, we removed the remaining prey from this platform. With two baited platforms per compartment, the bats could thus retrieve a maximum of 30 mealworms from a single compartment per session. The bats were prevented from perching inside the compartments by slowly approaching and gently touching them. To ensure sustained foraging motivation throughout data acquisition, the session was stopped when 45 mealworms had been eaten or 15 min had elapsed. The bats maintained or slightly increased their weight with a daily supply of 45 to 50 mealworms, which was a naturalistic amount of food.

Acquisition and analysis of behavioural data

Experiments were run in the dark and filmed (Sanyo BW CCD camera VCB-3572 IRP, Munich, Germany Computar lens M0518, Düsseldorf, Germany Sony recorder GVD1000E, Berlin, Germany) under IR-illumination (custom made IR-strobes) for online display and videotaped for later off-line analysis. For off-line analysis, we used an event-recorder software (Department of Animal Physiology, University of Tübingen) to extract the following parameters:(A) flight time spent in each compartment (B) number of flights into each compartment. Capture events were counted online and subdivided into (C)capture events per compartment and (D) capture events per compartment for the 25 first capture events. The latter measure was introduced because each bat in every session performed at least 25 capture attempts. As a maximum of 30 were allowed per compartment, these first 25 events could be allocated entirely to one compartment, i.e. noise avoidance could be especially pronounced.

The data were normalized and expressed as percentages for display and statistical analysis. Performance of each individual bat was averaged over the three replicas (experimental periods) for a given experimental condition(combination of stimulus type and stimulus compartment position, e.g. `traffic noise' played in the `left' compartment) for the statistical analysis. To account for possible individual differences, we used repeated-measures analysis of variance (ANOVA) and post hoc paired t-tests with sequential Bonferroni correction to test for the influence of playback treatment on the bats' behaviour. To test for possible preferences of the bats for one of the two test compartments, we included stimulus compartment position (left or right) as a factor into the ANOVAs. For testing, percentage data was transformed following Zar (Zar,1999) (p'=arcsin √p). Tests were run in SPSS 15.0.0 for Windows (SPSS, Inc., Chicago, IL, USA).

Recording, generation and playback of acoustic stimuli

Traffic noise was recorded at a distance of 7.5 m from the centre of the right lane of a highway and 1.5 m in height (Autobahn A8, Stuttgart-Munich,Germany recording location at 48 deg. 37'53.79N and 9 deg. 32'22.36 E). We recorded only when it was not raining and when the asphalt was dry. Recordings were taken on windless days therefore, no wind guard was used (which would have acted as an unwanted low pass filter). Passing vehicles were videotaped to determine vehicle type (car or truck) and to roughly estimate speed. The sound of the cars was picked up with a sensitive, broadband condenser measurement microphone for playback purposes (1/2″ low noise Microphone System Type 40HH, G.R.A.S., Holte, Denmark frequency response ±1dB between 0.5 and 10kHz ±8 dB between 10 and 50 kHz, internal noise floor 6.5 dBA re. 20μPa). To ensure a quantitative, broadband analysis of traffic noise, we used a slightly less sensitive but more broadband measurement microphone (G.R.A.S. 1/4″ 40BF free field microphone). The microphones were oriented perpendicular to the highway, i.e. we obtained on-axis recordings from passing vehicles. Signals were digitized viaa custom-built external A/D-converter (`PCTape' Animal Physiology, University of Tübingen, 16 bit depth, 8×oversampling, digital anti-aliasingsampling rate 192 kHz) and recorded online onto a laptop computer and stored as wav-files (custom-made recording software). From recordings of the passes of 50 cars and 50 trucks at speeds of approximately 80 km h –1 , we selected the loudest 500 ms window (maximum root means square (RMS) amplitude) with a custom Matlab (TheMathWorks, Inc.,Natick, MA, USA) routine. To measure the energy distribution over frequency,we computed power spectral densities (PSDs, FFT 256) in Matlab on these 500 ms windows. The average PSDs for these 50 cars and 50 trucks(Fig. 2) show that traffic noise has its main energy clearly within the human audio range but does contain ultrasonic components up to 50 kHz.

We recorded the sound produced by moving vegetation with the above described 1/2″ microphone and setup. As we faced a prolonged period without wind, we moved bundles of stalks in a dry reed bed by hand in an undulating way in order to simulate wind-induced movement. When the stalks and leaves of the dry reed touched each other, they produced series of broadband click-like and noise-like signals with energy ranging from 0 to frequencies higher than 85kHz (example in Fig. 3).

All playback files were arranged or generated in Adobe Audition 1.5(Adobe® Systems, Mountain View, CA, USA). Representative recordings of traffic noise and of moving reed vegetation were used. An empty wav-file(amplitude values of all samples at zero) was generated for the silence treatment. The broadband noise treatment was digitally generated using continuous white noise. The noise spectrum was subsequently altered due to digital filtering, the speaker characteristics and the transmission through air. As a result, the noise spectrum at the platforms was no longer `white'(i.e. all frequencies at equal amplitude). Higher frequencies were attenuated but were considerably more pronounced than in the traffic noise. All playback files had a sampling rate of 192 kHz, i.e. contained frequencies up to 96 kHz. All files were highpass-filtered at 1 kHz (Adobe Audition digital FFT filter,2048 points, Blackman window) to remove sound probably not audible to the bats and to avoid damage to the speaker. The playback amplitude of the digitally generated broadband noise was adjusted in such a way that incident sound measured 80 cm above the platforms had an SPL of 80 dB. This corresponds to the noise level 10–15 m next to a highway as a vehicle passes. The traffic playback files were digitally set at the same RMS sound pressure level for the loudest 500 ms window contained in the playback file (Adobe Audition Analyze). While the broadband noise remained constant at this level, the traffic noise oscillated around this level. The traffic noise would drop when no vehicle was travelling by the recording microphone and would rise in level for periods shorter than 500 ms when a vehicle passed. The playbacks of vegetation movement were set at 12 dB below the broadband noise and the traffic noise files however, the vegetation movement playbacks were still unnaturally loud or at least corresponding to movement induced by very strong wind as from a human perspective.

Mean power spectral densities (PSDs) for 50 cars and 50 trucks recorded at a highway in 7.5 m, 15 m and 25 m distance from the middle of the right lane. Microphone height was 1.5 m. Error bars display the standard deviation.

Mean power spectral densities (PSDs) for 50 cars and 50 trucks recorded at a highway in 7.5 m, 15 m and 25 m distance from the middle of the right lane. Microphone height was 1.5 m. Error bars display the standard deviation.

Files were played in a continuous loop throughout a trial. They were played back from a laptop through an external D/A-converter (RME Fireface 800 Interface, sampling rate 192 kHz, Haimhausen, Germany), broadband amplifiers(WPA-600 Pro, Conrad Electronics, Hirschau, Germany) and the above mentioned speaker.


Listening to these types of sounds may be the key to stress relief

Crickets chirping at night. The flow of water running through a river. A bird’s song first thing in the morning. The soundtrack of nature is ever-present but often drowned out by the rest of the modern world car horns, lawnmowers, and power drills.

Now, a new study suggests everyone should find some time to soak up the sounds of nature and nearby wildlife. This collaborative research project reports natural sounds to produce tangible health and wellness benefits. People who regularly hear such sounds typically experience less physical pain, lower stress, improved mood, and more robust cognitive performance.

Specifically, the sounds of water were found to be most helpful at encouraging improved moods and physical health outcomes. Bird songs and sounds, meanwhile, seem to offer the most help in regards to stress relief and instilling calmness.

This study was put together by Colorado State University, Michigan State University, Carleton University, and the National Park Service. Study authors analyzed sound recordings taken at 251 different locations across 66 US national parks.

Plenty of recent research over the past few years has concluded that humans benefit greatly from spending more time around nature, wildlife, and greenery. These findings are unique in the sense that one doesn’t have to physically enter nature to reap some of those rewards. Even if you live in the middle of Manhattan, all you need is a pair of headphones to escape the sounds of the city for a little bit.

“In so many ways the COVID-19 pandemic has emphasized the importance of nature for human health,” says co-lead study author Rachel Buxton, a post-doctoral researcher in Carleton’s Department of Biology. 𠇊s traffic has declined during quarantine, many people have connected with soundscapes in a whole new way – noticing the relaxing sounds of birds singing just outside their window. How remarkable that these sounds are also good for our health.”

Additionally, co-author and associate professor at MSU Amber Pearson brings up another fascinating point. The sounds of nature appear to have the exact opposite effect as more modern, industrial sounds. Plenty of research has found prolonged exposure to industrial and urban noises can be detrimental to one’s health.

“Most of the existing evidence we found is from lab or hospital settings,” she adds. “There is a clear need for more research on natural sounds in our everyday lives and how these soundscapes affect health.”

Of course, it’s always preferable if possible to physically visit natural spaces like a national park. On that note, though, study authors say some popular national parks located near urban areas may be too noisy due to heavy foot traffic.

“Park sites near urban areas with higher levels of visitation represent important targets for soundscape conservation to bolster health for visitors” explains study co-author Kurt Fristrup, a bioacoustical scientist at the National Park Service. “Nature-based health interventions are increasingly common in parks and incorporating explicit consideration of the acoustic environment is an opportunity to enhance health outcomes for people.”

So, the next time you visit a national park (or any park for that matter) try going off the beaten path for a little while and find yourself a quiet, secluded area. Close your eyes, and take in all of the sounds occurring around you for a few moments. Just a few minutes spent doing this may improve your mind and sharpen your thoughts for the rest of the day if not longer.

“The positive health impacts and stress reduction benefits of nature are more salient than ever to help offset the concerning increase in anxiety and mental health issues,” notes George Wittemyer, a study co-author and professor at CSU.

If you can find the time to visit a nearby park or another nature reserve, it’s a trip fully worth taking. But, if you can’t, consider swapping out a true-crime podcast or two for some nature recordings.

The full study can be found here, published in Proceedings of the National Academy of Sciences.


Bird calls were sweeter this spring, thanks to lockdown, says Science journal

Less noise during the lockdown restrictions, which were enforced in various parts of the world to contain the spread of the coronavirus disease (Covid-19) pandemic during this spring, may have allowed birds to sing sweeter and softer songs, according to a study published in the journal Science last week.

Ornithologists and birders reported hearing more bird songs and calls even from the species they had never heard before, but always knew were in the vicinity.

The study found that sparrows in the United States of America’s (USA) San Francisco Bay area responded to the new acoustic space during the lockdown in April and May by singing higher performance songs — those involving trills or other vocal ornamentation and at lower amplitudes.

Despite the reduced amplitude, communication distances more than doubled, which could both reduce territorial conflicts and increase mating potential, the study suggested.

Titled Singing in A Silent Spring: Birds respond to a half-century soundscape reversion during the Covid-19 shutdown. The study, led by the Department of Ecology and Evolutionary Biology at the University of Tennessee, USA, also found that the low-frequency noise generated by traffic and vehicle crossings in April and May returned to levels not heard since the 1950s.

Usually, birds that have breeding areas, where ambient noise is high, sing higher amplitude songs. This is called the Lombard effect, an involuntary vocal response to the presence of background noise, because people tend to speak louder in noisy environments.

The study revealed that male birds produce songs with higher minimum frequencies in areas with high energy. While low frequency noise is typical of traffic in urban surroundings.

The study concluded that birds managed to maximise communication and salience. “These findings illustrate that behavioural traits can change rapidly in response to newly favourable conditions, indicating an inherent resilience to longstanding anthropogenic pressures like noise pollution,” it said.

“This is interesting, but, perhaps, not unexpected. Birds can modulate their song amplitude in response to noise levels. One might expect them to lower amplitudes in quieter backgrounds. More interesting is that they could then use the energy saved to sing higher performance songs…we certainly had much less ambient noise in urban spaces in India as well, but to comment on how birds may have changed their amplitude or song structure will require quantitative data, which I do not have,” said Professor Rohini Balakrishnan of the Centre for Ecological Sciences at the Indian Institute of Science (IISc), Bengaluru, and a specialist in bio-acoustics.

Veteran ornithologist Asad R Rahmani, a former director of the Bombay Natural History Society (BNHS), said he could hear several species, despite living in a crowded part of Lucknow, where there are fewer trees, during the Covid-19-induced lockdown restrictions.

“I live in a crowded area, where there are not too many trees, bushes or shrubs. Nevertheless, during the lockdown when there was no traffic on the streets, I could hear Indian Cuckoo because March to June is its breeding season so it is very vocal, Greater Coucal, Laughing Dove, Jungle Babbler, Golden Oriole, Peafowl, Brown Rock Chat, Rose-ringed Parakeet, House Sparrow, Spotted Owlet, Indian Scops Owl (both at night), Brown-headed Barbet, Coppersmith Barbet, Black-rumped Flameback (woodpecker), Red-vented Bulbul, Common Iora, and a few other species of birds,” Rahmani said.

“The initial months of lockdown --- from March to June --- were the main breeding season when the males call and become territorial. They must have had a peaceful breeding season in which their calls were not drowned by the incessant noise of traffic, loudspeakers, and horns, which are all human creations,” he said.

However, the calls have stopped following the gradual easing of lockdown restrictions, he added.

In Gurugram, author and ornithologist Bikram Grewal said he heard birds which he knew were in the vicinity but hadn’t heard before the 68-day nationwide lockdown restrictions were enforced from March 25.

“It could just be that noise levels were low. As a result, we paid more attention. I heard the Ashy Prinia, Tailorbirds, Indian Grey Hornbill, Spotted Owlet and the Rufous Treepie from my house in Gurugram. We definitely heard bird calls and bird songs a lot more this spring,” Grewal said.

Some birders reported watching more birds in April and May.

“I live in suburban Bengaluru, where birdlife is already quite rich. There has been a further spurt in bird activity since the lockdown restrictions were lifted. They were exhibited in two distinct phenomena – an increase in birdsong and also an uptick in their presence,” said Ramki Sreenivasan, a Bengaluru-based wildlife photographer and co-founder, Conservation India.

“Notable examples are grey francolins (partridge) and peahen. Both are large birds and are, otherwise, wary of human presence. The peahens made their first visible appearance in the neighbourhood, thanks to the lockdown. I could see and hear them from my balcony. Birdsong moved to another level during the onset of monsoon. Either, there were more birds calling or we had just not heard them due to the traffic and ambient noise. For example, Ashy Prinias is always vocal wherever it is. But this monsoon the species of the bird erupted with incessant and loud vocal battles,” he added.

Anand Krishnan, a scientist at Indian Institute of Science Education and Research (IISER), Pune, who specialises in interdisciplinary studies of bird sensory signals, cautioned about several contradictory papers on the impact of noise on birdsong.

“This paper’s quantitative assessments are nice. However, the conclusions about amplitude changes are not novel in and of themselves. The effects of noise on birdsong are a field with many, often contradictory papers, and the effects on reproduction and behaviour are also still unclear. For example, it is difficult to tease apart the effect of noise on mating and reproduction versus say air pollution or other factors. Lower amplitude songs in lower noise are something called the Lombard effect, which is known in many birds. A lot more work is needed to show that birds are responding to the ‘new acoustic space’ versus other environmental changes. Where this paper differs is in taking advantage of a one-off ‘noise reduction,’ as opposed to comparing birds singing in more and less noisy areas,” he said.


Watch the video: 8 Hour Nature Sound Relaxation-Soothing Forest Birds Singing-Relaxing Sleep-Bird Chirping Sounds (June 2022).


Comments:

  1. Caindale

    That does not concern you!

  2. Phelot

    What touching words :)

  3. Alahhaois

    the Bossy point of view, amusingly ...

  4. Ramone

    Very amusing phrase

  5. Achcauhtli

    Wonderful, very funny idea

  6. Leandro

    Granted, this thought just got by the way



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