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Bird Song Changes Sound Alarm Over Habitat Fragmentation

New research published in the British Ecological Society's Journal of Applied Ecology has found that changes in bird song could be used as an early warning system to detect man-made ecological disturbances. Although much previous research has focused on bird song and vocal mimicry, this is the first study to analyze the role played by habitat loss and fragmentation on song-matching.

Ecologists recorded and analyzed the songs of more than 200 Dupont's larks in Spain and Morocco and found that in fragmented habitats, song-sharing among neighbors was enhanced, whereas song-sharing among non-neighbors declined. Having ruled out other explanations, such as the stage of the breeding season and competition intensity, the researchers say this change in song-sharing is due to lack of interaction between individuals isolated by habitat barriers.

This suggests that males from fragmented habitats perceived as rivals only the close neighbors with which they engaged in counter-singing.

"Because of their rapidly evolving cultural nature, bird vocalizations might become an early warning system detecting the effects of fragmentation over relatively short times and before other indicators - such as genetic markers - show any change," says the researchers.

Sharing song types - when a male replies to a rival’s song with the same song sequence - with neighbors is common in birds and is thought to act as a threat signal between males, which would explain why birds have evolved such complex song repertoires.

The Dupont's lark is a rare and specialized steppe passerine, and its song unit is made up of up to 11 discrete sequences, each sequence being composed of up to 13 notes. The most common sequence is known as the whee-ur-wheeee. To be considered as shared songs in this study, two sequences had to match at least 75 percent of their component notes and the matching portions had to be similar in note shape, timing, and frequency.

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