Birds in North America are getting smaller because of climate change

A study of nearly 40 years on tens of thousands of birds killed by flying high-rise buildings in Chicago (USA) found that their size diminishes over time due to climate change.

The study, published on Dec. 4, involved 70,716 dead birds between 1978 and 2016 during the spring and winter migration seasons each year in the third largest city in the United States.

The study recorded the body size of birds killed by flying into high-rise buildings in Chicago for nearly 40 years - (Image: REUTERS).

The results showed that the average body size of these birds became smaller over time although their wingspan increased.

Reuters said the researchers concluded that the warmer climate has made the size of certain birds in North America, and probably around the world, smaller.

The team relies on a phenomenon called Bergmann's Law , whereby individuals in a species tend to shrink in warmer and larger areas in colder regions, for the reason that species become small. Travel over time as the temperature rises.

The study focused on 52 species, most of which are songbirds such as sparrows, warbler, and thrushes, which are born in cold climates in North America and often live in southern areas. Chicago in the winter.

The study focused on 52 species of birds born in cold climates in North America - (Image: REUTERS).

For nearly 40 years, the body size of all 52 bird species in the study decreased. Their average body weight decreased by about 2.6%. The length of the leg bone is also reduced by about 2.4%. Wingspan increased by 1.3% with the ability for these species to continue long-distance migrations with smaller bodies.

"In other words, climate change seems to have changed the size and shape of these birds, " said University of Michigan research and biologist leader Brian Weeks.

"Everyone agrees that the climate is warming but examples of how this is affecting the natural world are now coming to light" - said Dave Willard of the team said.

The study provides new evidence for disturbing trends in North American birds. Another study published in September showed that the number of birds in the US and Canada has decreased by 29% since 1970, or about 2.9 billion birds.

"I think the message here is that when humans change the world at an unprecedented speed and scale, there will be consistent and wide-ranging reactions related to living things to adapt to environmental change. " - Mr. Weeks said.

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