DARWIN REVISITED: Rain forest birds are undergoing evolutionary morphological changes in order to adapt to climate change

Vitek Jirinec et al in Science Advances: 

https://www.science.org/doi/10.1126/sciadv.abk1743

LSU Media Center: 

AMAZON RAINFOREST BIRDS’ BODIES TRANSFORM DUE TO CLIMATE CHANGE

https://www.lsu.edu/mediacenter/news/2021/11/12rnr_jirinec_stouffer_scienceadvances.php

Amazonia is the world’s largest tropical forest located in Brazil and Ecuador. The avifauna consists almost exclusively of residents that spend their whole life in this region without needing to migrate or be subjected to stress from the ingression of migratory birds from other regions or to any other disturbance. 

Over four decades, the temperature has become gradually warmer in Amazonia. From June to November, the dry season, the climate has become increasingly hotter and drier. The birds have therefore been experiencing gradually warmer temperatures throughout their annual cycle and this is the sole and only change to their habitat.

“Even in the middle of this pristine Amazon rainforest, we are seeing the global effects of climate change caused by people, including us,” said Vitek Jirinec, lead author of the scientific publication.

The authors found that the birds had undergone a change in body weight: they have become smaller and lost weight. At the same time, their wing size has increased.

The LSU Media Center explains:

“The scientists investigated 77 species of rainforest birds that live from the cool, dark forest floor to the warmer, sunlit midstory. They discovered that the birds that reside in the highest section of the midstory and are the most exposed to heat and drier conditions, had the most dramatic change in body weight and wing size. These birds also tend to fly more than the birds that live on the forest floor. The idea is that these birds have adapted to a hotter, drier climate by reducing their wing loading therefore becoming more energy efficient in flight. Think of a fighter jet with a heavy body and short wings that requires a lot of energy to fly fast compared to a glider plane with a slim body and long wings that can soar with less energy. If a bird has a higher wing loading, it needs to flap its wings faster to stay aloft, which requires more energy and produces more metabolic heat. Reducing body weight and increasing wing length leads to more efficient resource use while also keeping cooler in a warming climate”.

As Charles Darwin stated nearly two centuries ago:

“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change”.

And that is what the Amazonia birds are doing in order to survive.