Climate change is causing birds to change their bodies


According to a new study by Louisiana State University (LSU) researchers, the most pristine areas of the Amazon rainforest, devoid of direct human contact, are influenced by man-made climate change.

Above the canopy of the Amazon rainforest where birds have gotten smaller and their wings have grown longer over generations, indicating a response to changing environmental conditions that may include new physiological or nutritional challenges. (Image credit: Vitek Jirinec, Louisiana State University).

The latest analyzes of data collected over 40 years reveal that not only have the number of susceptible local birds throughout the Amazon rainforest declined, but body sizes and wing lengths have become different for most of the species examined. These physical differences in birds gradually follow the dry and hot conditions of the dry season (June to November).

Even in the midst of this Amazon rainforest, we are seeing the global effects of climate change caused by people, including us.

Vitek Jirinec, lead author of the study and associate ecologist, Center for Research in Integral Ecology

Vitek Jirinec is a former student of LSU (Ph.D. ’21). This study was published in the journal Scientists progress.

Amazon rainforest birds have become smaller in size, and their wings have grown longer over generations, signifying a reaction to ever-changing environmental conditions that can include new nutritional or physiological issues.

This is the first research to determine these changes in body size and shape in non-migratory birds, which eliminates other factors that may have impacted these physiological alterations. Jirinec and his colleagues examined data collected on more than 15,000 individual birds that were captured, weighed, measured, tagged with a leg band and released – over 40 years of fieldwork in the world’s largest rainforest. world.

Data shows that about all bird bodies have shrunk in mass, or become lighter, since the 1980s. The majority of bird species have lost an average of about 2% of their body weight every 10 years. . For an average bird species that weighed around 30g in the 1980s, the population currently averages around 27.6g. How important is that?

These birds do not vary much in size. They’re quite refined, so when everyone in the population is a few grams smaller, that’s important.

Philip Stouffer, study co-author, Professor Lee F. Mason, School of Renewable Natural Resources, LSU

The dataset encompasses a large expanse of rainforest, so alterations in the body and wings of birds across communities are not fixed to a particular site, meaning the occurrence is universal.

This is definitely happening everywhere and probably not just with the birds … If you look out the window and consider what you see there the conditions are not what they were 40 years ago and it it is very likely that plants and animals will react to these changes as well. We have this idea that the things we see are fixed in time; but if these birds are not fixed in time, it may not be true.

Philip Stouffer, study co-author, Professor Lee F. Mason, School of Renewable Natural Resources, LSU

Researchers examined 77 species of rainforest birds that reside in cool, dark forest floors through to warmer, sunny surroundings. They learned that birds that live in the highest part of the middle, and which are most exposed to heat and drier environments, had the most marked change in wing size and body weight. These birds are also prone to fly more than the birds that reside on the forest floor.

The impression is that these birds have adapted to a warmer, drier climate by minimizing their wing load, thus becoming more fuel efficient when in flight. Much like a fighter plane, with a heavy body and short wings that require a lot of energy to fly fast compared to a glider with a thin body and long wings that can fly with minimal energy.

If a bird has a higher wing load, it has to flap its wings faster to stay aloft, which requires more energy and generates more metabolic heat. Reducing body weight and increasing wing length allows for more competent use of resources while staying cool in a warming climate.

Former LSU student Ryan Burner (Ph.D. ’19) has done much of the analysis that has revealed the disparity between bird flocks over the years. Burner, who is currently a wildlife biology researcher at the US Geological Survey Upper Midwest Environmental Sciences Center, is the study’s second author.

The question of the future capacity of Amazonian birds to cope with increasingly hot and drier environments, especially in the dry season, remains unresolved. The same problem can be linked to many places and species that reside on the fringes of even greener extremes.

There may be other researchers in other places who have relevant data from the 1970s and 1980s that could be compared to modern data, because the bird banding protocol we used is pretty standard.

Philip Stouffer, study co-author, Professor Lee F. Mason, School of Renewable Natural Resources, LSU

“So if you measure the mass and the wing, maybe there will be more data sets that emerge and we can get a better idea of ​​the variation in space and how that might change in the space. different systems. “ Stouffer added.

Journal reference:

Jirinec, V., et al. (2021) Morphological consequences of climate change for resident birds in the intact Amazon rainforest. Scientists progress.



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