Birds are shrinking. These scientists say it's a consequence of global warming.

https://www.washingtonpost.com/science/2019/12/04/birds-are-shrinking-these-scientists-say-its-consequence-global-warming/

By Ben Guarino, Dec. 4, 2019 at 8:00 a.m. CST

Birds are getting smaller. So shows an analysis of migratory birds that died after colliding into buildings in Chicago and were collected as specimens for the Field Museum of Natural History.

David Willard, a Field Museum ornithologist, has measured the Windy City’s dead birds since 1978. Data from his calipers and scales reveal decades-long trends in bird bodies: Their legs, on average, are growing shorter. They have lost weight. Their wings are getting slightly longer.

These changes are present in nearly all of the species he measured, according to a study of 70,716 bird specimens from almost 40 years published Wednesday in the journal Ecology Letters. Morphing birds, Willard and his colleagues say, reflect a changing climate.

“Warming temperatures seem to be having a pretty consistent and almost universal effect on a large number of different species, regardless of other aspects of their biology,” said study author Benjamin Winger, who studies the evolution and ecology of birds at the University of Michigan.