Birds sing at sunrise to defend their territory and communicate about food: Study

Time of India

15 hours ago

Pune: Birds in the Western Ghats begin their day with a chorus of songs, mainly to protect their space and share important messages like food locations, a study has found.
The study conducted in Valparai plateau in the Western Ghats by scientists Vijay Ramesh, Pavithra Sundar, and Meghana Srivathsa from the Cornell Lab of Ornithology and Project Dhvani showed that highly territorial birds sing loudly at dawn to warn others to stay away.
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Some birds also use their morning songs to help their groups stay connected and informed, especially those that eat a mix of insects and fruits.
The researchers placed audio recorders at 43 different rainforest sites to capture bird sounds and studied them between March 2020 and January 2021. The team listened closely to bird calls at dawn and dusk. Of the 120 species recorded, they focused on 69 commonly heard species.
Among the birds most active at dawn were the Indian blackbird, little spiderhunter, oriental magpie-robin, and purple sunbird. These birds were often heard in the morning and, to a lesser extent, in the evening.
The study was published in the Royal Society journal Philosophical Transactions on June 12.
Ramesh said, "Bird species vary widely in their diurnal vocalisation patterns, and the drivers of this variation are not well understood.
Using passive acoustic monitoring, we examined species-specific vocal activity patterns at dawn and dusk for a tropical bird community in the Western Ghats biodiversity hotspot in India."
The scientists tested whether environmental factors such as signal transmission conditions, ambient light, and resource availability, and social factors such as territoriality, best explained patterns of diurnal variation in vocal activity.
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Using multiple autonomous recording units collecting data across numerous locations simultaneously, they can now obtain large amounts of species-specific acoustic data for an entire community.
The Western Ghats is home to hundreds of bird species, several of which are rare, endangered, and endemic to this region.
The Valparai plateau is situated in the Anamalai hill range within the Western Ghats and primarily consists of mid-elevation tropical wet evergreen rainforests.
The plateau is a typical example of a human-modified biodiverse landscape in India and is home to hundreds of species of rare and endemic flora and fauna and supports the livelihoods of thousands of people.
Sundar, another scientist who was part of this study, said, "We found that highly territorial birds and omnivorous species were much more likely to be active singers during dawn hours."
The authors of the research paper stated that early morning hours were important for territorial species to protect their locations.
Species that eat insects and fruit—that is, omnivores—also showed a prevalence for singing more at dawn. Sundar said these species were often members of mixed species foraging flocks, in which vocal communication was essential for finding food and for warning group members about potential predators nearby.
However, additional research that includes visual observations is needed to confirm this speculation, Ramesh said.
The researcher stated that this study helped them understand how birds communicated and how changes in the environment could affect their natural behaviour. "By listening carefully to nature, researchers are learning not just when birds sing, but why it truly matters," stated Ramesh.
Acoustic signals of four species were detected only at dawn—the Indian blackbird (Turdus simillimus), the little spiderhunter (Arachnothera longirostra), oriental magpie-robin (Copsychus saularis), and the purple sunbird (Cinnyris asiaticus).
Twenty species had vocal activity that was substantially higher at dawn.
Notable representatives include the grey-headed canary-flycatcher (Culicicapa ceylonensis), greater coucal (Centropus sinensis), large-billed leaf warbler (Phylloscopus magnirostris), and puff-throated babbler (Pellorneum ruficeps).
The dark-fronted babbler (Rhopocichla atriceps) was the only species with significantly higher vocal activity at dusk.