The nightingale famed for its beautiful songbird was feted by John Keats as a "light-winged Dryad of the trees." But this much-celebrated small bird may be increasingly endangered as its wings slowly shrink in response to climate change, according to a new study.
Scientists warn that this change will make its long migrations more difficult and could threaten its very survival. This little bird makes an epic migration from sub-Saharan Africa to go to its European breeding ground each summer but only 7,000 nesting pairs are left in England.
The song of the nightingales may soon become harder to hear as their numbers fall dramatically over the recent decades largely due to climate change. Males, particularly are known to sing for hours on end every night during the breeding season.
Maladaptive Evolution
According to zoologist Carolina Remacha of the Complutense University of Madrid, there is much evidence suggesting that because of the changes in the climate over the last few decades it has affected the migratory birds' arrival and laying dates, and as well as the physical features of nightingales.
Remacha's team has analyzed a twenty years' worth of data on the birds and found that natural selection driven by climate change caused the nightingale to evolve into having shorter wings, which could make them less likely to live throughout their journey on their annual migration.
They compared two populations of nightingales from central Spain and discovered the bird's average wing length is now shorter relative to its body size. Shorter-winged nightingales were less likely to return to Europe -their breeding ground- after their first round-trip to the African continent.
Experts call the evolving of smaller clutch sizes and inadvertently shorter wings a 'maladaptation' in which it reduces the nightingale's chance of surviving. In this situation, instead of being useful the bird's responses to changing conditions have become harmful to them.
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But why?
Scientists believe that the changes in the physical features of the bird are due to the changes in temperatures seen in the Mediterranean region. The spring is delayed and the intensity of summer drought is higher which could result in a shorter optimal breeding period for the birds and possibly favoring shorter wings for the nightingale birds, said Remacha.
Nightingale usually adjusts to the demands of migration by having longer wings and larger clutch sizes but a shorter lifespan. However, the changing climate interferes with this and demands a response from the birds.
Although it may come at a price, the most successful birds are having smaller families and smaller wings to adjust with a shorter breeding season.
Professor Javier Pere-Tris, co-author and also from Complutense University said, "if these changes are the response to the new environment, then obviously the ones that have been selected, the ones with shorter wings, are the optimal nightingales for the new situation."
However, these are not the best wings for migration. The birds who continue the same migration patterns and destinations are mostly like have a lesser chance of survival.
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