Tag Archives: bird vocalization

Birds change song to be heard above traffic noise

(Julia John 2 may 2017; Photo Kelly Colgan Azar )

Vehicles are a major source of noise pollution for urban wildlife. That’s particularly a problem for birds that have to compete with the roar of engines to communicate. Recent research from Washington, D.C., suggests that some birds —those with innate rather than learned songs —modify their song structure to be heard over the din of traffic.

In noisier conditions, these birdsongs are shorter and have a smaller range of frequency, said Katherine Gentry, lead author on the paper published in Bioacoustics. The birds raise their minimum frequencies, reducing their song’s overlaps with low frequency traffic noise.

“That makes it easier for the receiver to detect the signal against the background noise,” said Gentry, a research assistant at George Mason University.

Gentry wanted to see if suboscines, a family of birds whose song is innate rather than learned, could adjust their signal to communicate over traffic noise. Suboscine species include the vermilion flycatcher (Pyrocephalus rubinus), chocolate-vented tyrant (Neoxolmis rufiventris), white monjita (Xolmis irupero) and eastern wood pewee (Contopus virens). Although many studies have examined birds’ response to noise pollution from vehicles, this was the first to look at how suboscines in particular change their song in the absence of traffic during temporary road closures.

Gentry recorded the song of the eastern wood pewee in Rock Creek Park, a large urban park in Washington, D.C. She then compared recordings from times when traffic noise was high and times it was low, including weekends, when roads were closed to vehicles to allow for cycling and joggers. “This study showed that suboscines can adjust their song as traffic noise fluctuates,” Gentry said. That’s good for the birds in that it allows them to improve their chances of successful communication, she said.

“Even though they’re improving the likelihood of signal reception, they’re potentially sacrificing the sexiness of their song,” Gentry said. “With that minimum frequency raised, they’re not singing that naturally selected song structure.”

Songs with a higher minimum frequency that have a narrower range of frequencies could negatively influence the birds’ ability to defend territories, find mates and reproduce if females and rival males respond more strongly to signals with wider bandwidths.

But Gentry also found that when the roads were closed and it was quieter, the birds sang more naturally. Even though a permanent reduction in traffic noise is most ideal, she said, road closures could benefit birds like these that alter their songs in response to higher traffic noise levels.

“Noise is an issue for animals,” Gentry said. “Even if they cope through signal adjustment, it could be affecting them in the long run. It’s important we make every effort to reduce it. It would be a broad benefit for the community.”

Research teaches machines to decipher the dawn chorus

(Author: Physorg; Photo: Wikipedia; 20 March 2017)

Innovative research looking at the timing and sequence of bird calls could provide new insight into the social interaction that goes on between birds. It will also help teach machines to differentiate between man-made and natural sounds and to understand the world around them.

The work is being led by Dr Dan Stowell, a research fellow in machine listening at Queen Mary University of London (QMUL). It is supported through an Early Career Fellowship from the Engineering and Physical Sciences Research Council (EPSRC). An audio slide-show Deciphering the dawn chorus on this research is available on YouTube with examples of the bird recordings.

In August 2015, Dr Stowell’s technology was released to the public in a smartphone app called Warblr. Users record the sound of a bird on their mobile device and the app analyses the sound, matches it with patterns of bird calls in its dataset and provides a list of possible species that the recording matches.

Dr Stowell is now building on this work to take the computer analysis of the sounds that birds make to a new level, to discover more about what messages are being communicated and who is dominating the conversations that are going on.

“Traditionally you would take explicit measures of things like how long is this sound, what frequency is that sound?” says Dr Stowell. “To go beyond this we use modern machine-learning methods where you don’t necessarily know how a computer has made a decision about a particular sound, but by training it, which means showing it lots of previous examples, we can encourage a computer algorithm to generalise from those.”

At the University’s laboratory aviary, female zebra finches provide Dr Stowell with plenty of audio examples for his work.

“We have put the timing of the calls together with acoustic analysis of the content of the call, for instance whether it is a short or long call. We examine factors such as does the probability of one bird calling increase or decrease after another bird calls or is there a more subtle interaction going on? Working out how strongly each bird influences another helps us to build a picture of the communication network that is going on in that group of birds.”

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The tiny corner of Asia where an Endangered songbird is thriving

(Alex Dale, 23 Feb 2017)

But unfortunately, it’s this same rich, powerful melody which is threatening to silence the species forever. As we reported during our 2016 Red List coverage, keeping songbirds as pets is an integral part of South-East Asian culture. In Indonesia in particular, streets are lined with chirping cages, and songbird contests are big business.

But as the streets grow louder, forests are falling silent. The widespread trapping of wild songbirds to meet demand for local bird markets, is driving many species endemic to the area towards extinction – with the prized Straw-headed Bulbul one of the more badly affected.

“Across much of Southeast Asia, the Straw-headed Bulbul has been relentlessly trapped from the wild to be later sold in the bird markets of Java, Kalimantan, Sumatra and Peninsular Malaysia,” says Yong Ding Li from The Australian National University. “The bird has gone extinct from Thailand and most parts of Indonesia where it used to be found, including the whole island of Java. Its populations have also collapsed across Malaysia.”

Check out its song in the video below:

However, there is one small haven where the Straw-headed Bulbul’s presence isn’t just stable, but actually growing louder: Singapore.

This is according to findings from a recent study led by Ding Li, and published in the journal Bird Conservation International. The study saw authors from The Australian National University and Nature Society (BirdLife in Singapore) gather data from more than 15 years of the Annual Bird Census, a yearly bird survey organised by Nature Society.

The result was an encouraging discovery: wild populations of the Straw-headed Bulbul have steadily risen in Singapore over that time period, and the country is now something of a global stronghold. Indeed, Singapore might now harbour more Straw-headed Bulbuls than anywhere else on the planet.

The increases were not noted on mainland Singapore, however, where populations merely remained stable – although given the Straw-headed Bulbul’s plight elsewhere, even this is a big win. Rather, the increases were documented on the small island of Pulau Ubin, situated north-east of mainland Singapore, and one of the country’s last remaining rural areas. Here, the species’ population increased by nearly 4% a year.

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