19 Jun Birds are getting increasingly smaller and you’ll never guess why

Here’s what the science says
Birds throughout the world have been getting smaller and it has a lot to do with climate change and the shifting temperature according to a study that was published in 2021.

Smaller birds are shrinking faster!
However, brand new research from a group of Yale University scientists has found that smaller birds are actually shrinking in size much faster than their larger counterparts. So what’s going on? Why are birds getting smaller and why are the tiniest most affected?

We’ve known for a while
Scientists have known since at least 2021 that something weird has been going on with the world’s bird populations when a study found a major decrease in their body sizes.

Four-decades of information
Published in the journal Science Advances, this study found that every single one of the 77 different Amazonian bird species they looked at over a four-decade period had a lower mean mass, meaning they had shrunk in size.

The results were a little complicated
But the results of the research weren’t as clear-cut as they sounded, though. While the bodies of the birds studied may have gotten smaller, the researchers found their wing spans had actually got larger.

Global temperatures were the main cause
The reasons why the birds’ bodies had gotten smaller and their wings had gotten bigger were initially varied but the researchers eventually concluded that global temperature changes played the most important role in changing bird sizes

Precipitation and climate change
“After accounting for other factors, the researchers found that the birds’ bodily changes were closely linked to the rising temperatures and shifts in precipitation caused by climate change,” wrote Audubon Magazine’s Lauren Leffler.

Increased pressures
Moreover, the study’s authors noted in their abstract that their findings could also be attributed to increased pressures that result from warming and added that seasonal and long-term bird sizes were a response to climate change.

Bergmann’s rule
One explanation put forth by the study’s authors was that the changes in the birds they studied may have been due to Bergmann’s rule, which Lauren Leffler defined in detail in her article explaining the 2021 study.

Warm-blooded animals get smaller to stay cooler in hot climates
“In biology, Bergmann’s rule posits that warm-blooded animals are larger in colder climates and smaller in warmer ones,” Leffler wrote. “That’s because larger bodies conserve heat, while smaller bodies disperse it more quickly.”

Is Bergmann’s rule an explanation for increased wing size?
“Bergmann’s rule also explains why a small cup of coffee cools down faster than a large one: Smaller objects have a higher ratio of surface area to volume, which means more contact with cooler air that absorbs heat,” Leffler added, and that might explain why wingspans increased.

76% of bird fit the rule
The 2021 study’s authors noted that 76% of the birds they looked at fit into Bergmann’s rule, especially those that were considered sedentary. But the rule didn’t explain everything.

A second look at bird body sizes
Scientists from Yale wanted to investigate these changes in the sizes of today’s birds and looked at the same four-decade period of information as the 2021 study as well as a second unrelated data set to look at body size changes in several different species.

129 different species are getting smaller
By analyzing both sets of data the Yale researchers were able to show changes in 129 different species they studied and found something shocking: smaller birds were shrinking much faster.

Smaller birds are shrinking faster
The researchers weren’t able to explain why small birds were shrinking faster than their larger counterparts but they were able to rule out a hypothesis that a particular species’ generational lifespan played a role in their changing body sizes.

The “primary mediator”
The researchers concluded that body sizes in bird populations appeared to be the “primary mediator” in a species’ response to climate change and added that this should be taken into consideration when trying to understand what’s changing bird sizes.

Original Article: https://www.msn.com/en-au/news/other/birds-are-getting-increasingly-smaller-and-you-ll-never-guess-why/ss-AA1bS0Wp