Ledgers recording body size measurements, measuring tools and a Tennessee Warbler belonging to Field Museum scientist, Dave Willard, who took measurements of 70,716 bird specimens of migratory birds that died in collisions with buildings in Chicago over a period of about four decades are pictured in this photo released on December 4, 2019. Field Museum/Kate Golembiewski/ Handout via REUTERS
WASHINGTON (Reuters) – Since 1978, researchers have scooped up and measured tens of thousands of birds that died after crashing into buildings in Chicago during spring and fall migrations. Their work has documented what might be called the incredible shrinking bird.
A study published on Wednesday involving 70,716 birds killed from 1978 through 2016 in such collisions in the third-largest U.S. city found that their average body sizes steadily declined over that time, though their wingspans increased.
The results suggest that a warming climate is driving down the size of certain bird species in North America and perhaps around the…