After studying the behavior of 69 species of birds in different regions of the Western Ghats in India, an international team of scientists was finally able to explain why birds sing most often at dawn. About this informs Philosophical Transactions of the Royal Society.
The Western Ghats mountain range, located along the western coast of India, is a UNESCO World Heritage Site and home to more than 500 species of birds. That is why scientists from the Lisa Young Bioacoustics Center at the Ornithology Laboratory of Cornell University (USA) together with colleagues from the Indian Dhvani project chose this region for research.
To find out why some species sing more in the morning and others in the evening hours, the team led by Vijay Ramesh applied passive acoustic monitoring – dozens of microphones were installed in the forest to automatically record sounds. At 43 points in the Western Ghats, scientists recorded birdsong for several months, collecting more than 40,000 hours of audio recordings and analyzing the behavior of 69 species.
The researchers also tested four main hypotheses explaining dawn singing: acoustic efficiency (better sound propagation with less wind and stable temperature), illumination (activity with the first rays of the sun), foraging (coordination of actions during feeding). According to the results of the study, it was found that 20 species sang much more actively at dawn, including the grey-headed canary flycatcher (Culicicapa ceylonensis), species of drongo (Dicrurus) and magnirostris. Instead, only one species sang in the evening – the black-headed babbler (Rhopocichla atriceps).
The reason for the morning singing turned out to be social factors: territorial and omnivorous species sang more often at dawn. This is because omnivorous birds usually forage in flocks, exchanging sound signals, including warnings of danger. At the same time, the factors of lighting, temperature and acoustics of the environment did not have a significant effect on the time of vocalization.
The obtained results cast doubt on traditional ideas about the reasons for the morning singing of birds. The authors emphasize the importance of taking into account the behavioral and social aspects of the life of birds. Further research using passive acoustic monitoring and visual observations will help to better understand patterns of bird vocalizations in different parts of the world.
