Pollution forces birds to change their tune


London : A new study reveals that male wild birds exposed to pollution develop more complex songs, preferred by the females, though they show reduced immunity.

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Katherine Buchanan and her colleagues at Cardiff University came to this conclusion after studying male European starlings (Sturnus vulgaris) foraging at a sewage treatment works in southwestern Britain.

Analysing earthworms that constituted their prey, the researchers found that birds exposed to greater pollution developed longer and more complex songs compared to a control group male birds.

Specifically, birds dosed with the complete spectrum of endocrine disrupting chemicals found in their prey spent a longer time singing, producing more complex songs, a sexually selected trait instrumental in attracting females for reproduction.

Researchers also found that the high vocal centre (HVC), the area of the brain that controls male song complexity, was significantly enlarged in contaminated birds.

Oestrogen causes masculinisation of the songbird brain and the HVC is enriched with oestrogen receptors. Neural development is thus susceptible to exposure to chemicals that mimic oestrogen, or to enhanced oestrogen levels. The results also confirm the plasticity of the adult songbird brain.

The scientists also found that female starlings prefer the song of males exposed to the mixture of endocrine disrupting chemicals, suggesting the potential for population level effects on reproductive success.

“This is the first evidence that environmental pollutants also paradoxically enhance a signal of male quality such as song,” said Katherine Buchanan, co-author of the paper.