How does the bird adapt to changes in its environment?

Like animals, birds too bear the brunt of climate change. Previous studies have shown how climate change affects birds migration, nesting, hatching and feeding habits. A recent study has shown how birds are evolving to develop smaller bodies and longer wingspans in order to adapt to the changes.

Published in the journal Science Advances, the study analysed the body size of birds in the Amazonian rainforest. Researchers analysed data collected on more than 15,000 birds that were caught, measured, weighed, and tagged over the course of 40 years of field work. In all, the scientists investigated 77 species whose habitats ranged from the cool, dark forest floor to the sunlit warm areas.

Lighter, but longer

Researchers found that nearly all the birds had become lighter since the 1980s. Most species lost an average of two per cent of body weight every decade, meaning a bird species that would have weighed 30 grams in the 1980s would now average 27.6 grams. A third of species simultaneously had developed longer wings, driving a decrease in mass to wing ratio. The birds that are known to fly more and are exposed to heat for longer, had the most pronounced changes in body weight and wing size.

But why?

The changes are thought to be a response to nutritional and physiological challenges, especially during the June to November dry season. The team hypothesised that this was an adaptation to utilise their energy better as they are now forced to travel longer to find food and shelter. Climate change has decreased the availability of fruit and insect resources for birds.

Longer wings, and a reduced mass-to-wing ratio, produce more efficient flight similar to how a glider plane with a slim body and long wings can soar with less energy.

A higher mass-to-wing ratio requires birds to flap faster to stay aloft using more energy and producing more metabolic heat Reduced size is perhaps beneficial under climate warming as the birds can cool themselves better. The data was not tied to a specific site but rather collected from a large range of the rainforest, meaning the phenomenon is ubiquitous. Researchers expressed that even the wildest parts of the Amazon untouched by humanity are being impacted by climate change.

Picture Credit : Google

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