Birds are shrinking and climate change is to blame

Amazonian birds have adapted their bodies to rising temperatures: climate change is making them shrink.

Climate change is the crisis that puts our, the planet's and animals' future at risk. It has already had many consequences, on ecosystems but also on animals. And on birds in particular. And scientists have recently discovered another one, in an area of the planet that we hoped would be immune to these disasters: the Amazon rainforest.

What's happening to the birds of the Amazon rainforest

It's a study that scientists have been carrying out for many years: since 1980 they have been capturing birds in the Amazon rainforest, putting an identification tag on their leg to catalog them and then releasing them into their environment. They have carried out this procedure on 15 thousand non-migratory birds of 77 different species.

Analyzing the data, the scientists found that almost all the birds have shrunk, and their bodies have become 2% lighter every ten years. To be clear, a species that weighed 30 grams in 1980 now weighs 27.6 grams. In some species, the reduction was even greater.

"These are birds that don't vary much in size within the species," explains Philip Stouffer, one of the authors of the research. "There aren't larger specimens and smaller specimens, so when they all decrease in weight then we have a problem."

The role of climate change

Since 1980, the average temperature on Earth has increased, and that's happened even in areas of the Amazon rainforest, where it has risen by 1°. In fact, the most significant changes in weight have been discovered in birds that live higher up in the branches of trees, and are therefore more exposed to the heat and rays of the sun.

Their bodies have decreased in weight and their wings have become larger-a way to make themselves more efficient in flight. Scientists think this is a way to adapt to an environment that has become increasingly humid: since 19996, rainfall has increased by 13%.

This would have made finding food more difficult, and so the birds would have needed a more efficient body that was easier to handle. Smaller bodies and larger wings also needed less heat production from metabolism for sustenance. One of the ways birds developed to adapt and make survival easier.