In the last forty years, human-induced climate change has not only reduced the number of birds in the Amazon rainforest, but has also changed their size: they have become smaller and with longer wings.

This is warned by a study, published this Friday in Science Advances, that explains that these Physical changes, that have been produced over several generations, they have helped the birds adapt to the increasingly hot and dry conditions of the dry season (June to November).

“Even in the middle of the pristine Amazon rainforest, we are seeing the global effects of climate change caused by people,” he warns. Vitek Jirinec, ecologist at Louisiana State University (LSU) and lead author of the study. The specialist was the first to discover changes in the size and shape of the bodies of non-migratory birds.

To do the study, the authors analyzed data from more than 15,000 birds captured, measured, weighed, tagged and released in the Amazon in the last 40 years.

The data showed that, since the 1980s,almost all bird bodies have reduced in mass or become lighter and most species have lost an average of 2% of their body weight each decade. For a species that weighed about 30 grams in the 1980s, the population now weighs an average of 27.6 grams.

In addition, the data was collected over a wide area of ​​the rainforest, showing that changes in birds They are not confined to a specific site but are a “significant and widespread” phenomenon that probably affects not only birds.

“If you look out your window and think about what you are seeing, you will see that conditions are not those of 40 years ago and it is very likely that plants and animals are responding to these changes,” he reasons. Philip Stouffer, LSU researcher and study co-author.

The scientists investigated 77 species of tropical rainforest birds who live from the cool and dark forest floor to the warmest and sunniest forest and discovered that those that reside in the highest part of the understory and are more exposed to heat and drier conditions, presented more drastic changes in their weight and on the wings.

The authors believe that birds have adapted to a warmer and drier climate by reducing the load on their wings (weight) and lengthening their length to be more energy efficient in flight. It is their way of adapting to climate change, but will they be able to cope with an increasingly hot and dry environment? That question remains unanswered, the authors conclude.

Even the most remote areas of the Amazon, where humans have not reached, are being affected by climate change.

Birds in the highest layers, which fly the most and are exposed to the most heat, recorded the most pronounced changes. in body weight and size of the wings.

The team hypothesized that it was an adaptation to the energy pressures, for example, decreased availability of fruit and insect resources, and also heat stress.

The longest wings and a reduced mass-to-wing ratio produces a more efficient flight, similar to that of a glider plane, which can fly using less energy.

A higher mass-to-wing ratio requires the birds to flap faster to stay aloft, using more energy and producing more metabolic heat.

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