Birdsong not just for the birds

July 28, 2008

Switch on the mike, start the recording, the stage is set for the local fauna! Computer scientists from the University of Bonn, in conjunction with the birdsong archives of Berlin's Humboldt University, have developed a kind of 'Big Brother' for birds.

This has nothing to do with entertainment, but a lot to do with the protection of nature. The new type of voice detector involved can reliably recognise the characteristic birdsong of different species of birds, thereby facilitating surveys of the bird population.

Europe's forests are falling silent as countless species of birds go on the red list of endangered species. Yet in fact no-one can say what the exact position is with some species. So as to have a reliable count of the territories of indigenous birds it would practically be necessary to send out a whole horde of spare-time ornithologists to count the birds. What is more, since the birds are often hidden in the undergrowth or the tree tops, ornithologists need to rely on their ears and their specialist knowledge. This means that in many areas it is wellnigh impossible to map the bird population comprehensively and continuously.

In view of such problems environmental protection has to fall back on new technical methods. Some of these are now being provided by Bonn scientists. Computer scientists from the University of Bonn have developed detectors which can recognise birdsong automatically. What this implies is that in the preliminary stage microphones are placed at selected points in the wild; these record all the sounds made, in some cases over a period of months. The new computer software can then sift through the many hundreds of hours of recorded material overnight and say how many birds of which species have been singing and how often they have been doing this.

In his project Daniel Wolff of the Institute of Computer Science at the University of Bonn initially concentrated on the bio-acoustic recognition of the Savi's warbler and the chaffinch. He listened carefully to the various types of birdsong, scrutinised them in a spectrogram and transferred the characteristics to algorithms. As soon as specific parameters are met, the programme kicks in. 'For example, the signal of the Savi's warbler has a mean frequency of 4 kHz, which is very typical. If, in addition, individual elements of the signal are repeated at a frequency of 50 Hz, this is detected as the call of a Savi's warbler,' Daniel explains. The chaffinch detector also analyses periodic repetitions of elements like these. In doing so it reveals more of a typical verse structure than the pitch of the chaffinch's song.

The Savi's warbler detector, particularly, which was subjected to long-term monitoring at Brandenburg's Parsteiner Weiher, is characterised by what researchers call 'robust recognition', i.e. a high degree of reliability. Despite interference from rain, wind and amphibians the programme recognised, with a 92% detection accuracy, the song of a species of bird which is still found on the shores of the Baltic but which has become rare elsewhere in Europe.

The birdsong detectors are as yet only calibrated for the birdsong of individual species. However, in the near future, Daniel Wulff thinks, it will be possible to link them up to a kind of superdetector which can recognise as many species as possible and, in combination with GPS coordinates, will make the mapping of bird populations simpler and more efficient.

The research field of bio-acoustics, he adds, is currently experiencing a boom. Although it was in the 1970s that the first attempts were made 'to detect the chaffinch with much slower computers,' Daniel says, with a nostalgic smile, 'what is decisive is that it's only now that we are in a position to store a large amount of recorded sound and place compact technology in nature which can really run for months, e.g. with solar energy.'

Source: University of Bonn

Explore further: How human language could have evolved from birdsong

Related Stories

How human language could have evolved from birdsong

February 21, 2013

"The sounds uttered by birds offer in several respects the nearest analogy to language," Charles Darwin wrote in "The Descent of Man" (1871), while contemplating how humans learned to speak. Language, he speculated, might ...

Genes tell story of birdsong and human speech

December 11, 2014

His office is filled with all sorts of bird books, but Duke neuroscientist Erich Jarvis didn't become an expert on the avian family tree because of any particular interest in our feathered friends. Rather, it was his fascination ...

World's least known bird rediscovered

January 25, 2010

A species of bird, which has only been observed alive on three previous occasions since it was first discovered in 1867, has been rediscovered in a remote land corridor in north-eastern Afghanistan. The discovery was made ...

Recommended for you

Amazon deforestation leaps 16 percent in 2015

November 28, 2015

Illegal logging and clearing of Brazil's Amazon rainforest increased 16 percent in the last year, the government said, in a setback to the aim of stopping destruction of the world's greatest forest by 2030.

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.