North American migratory birds have been getting smaller over the past four decades, and their wings have gotten a bit longer.
North American migratory birds have been getting smaller over the past four decades, and their wings have gotten a bit longer. Both changes appear to be responses to a warming climate.
Those are the main findings from a new University of Michigan-led analysis of a dataset of some 70,000 North American migratory birds from 52 species that died when they collided with buildings in Chicago.
Since 1978, Field Museum personnel and volunteers have retrieved dead birds that collided with Chicago buildings during spring and fall migrations. For each specimen, multiple body measurements are made.
The research team analyzed this remarkably detailed dataset to look for trends in body size and shape. The biologists found that, from 1978 through 2016, body size decreased in all 52 species, with statistically significant declines in 49 species.
Read more at University of Michigan
Image: University of Michigan biologist Brian Weeks, lead author of a new study on avian responses to climate warming. (Image credit: Brian Weeks)