Researchers at the University of Michigan are trying to connect the dots between birds becoming smaller with longer wings and their earlier migration.
Studies have shown birds are migrating here earlier in the spring. Other studies show they have been physically changing over the decades. Both are due to climate change, according to studies.
“On one hand, these birds are dramatically changing in their size and shape, and on the other, they were also changing the timing of their migrations,” said Marketa Zimova, lead researcher in a study to determine if the two were connected.
“So we expected that those birds that were able to increase their wings the most over the past 40 years would be able to advance their migration the most,” she said.
But the researchers got a surprise.
“There was absolutely no correlations between these two variables,” Zimova said.
Of the 52 species studied, there was no direct correlation between how much birds had physically changed and how much earlier they began migrating, which was surprising.
The scientists based their study on birds that had collided with skyscrapers in Chicago and died. The Field Museum has an extensive collection of the birds collected at the base of the buildings. (See here why birds collide with buildings.)
Zimova and her co-authors, Ben Winger and Brian Weeks, both from the University of Michigan, say now it’s a matter of finding other reasons that might account for the separate changes.
The research is in today’s Journal of Animal Ecology.