What Dead Birds Can Tell Us About Climate Change

shrinking birds
The Field Museum’s total bird collection has about half a million birds that date back to the middle of the 1800s. The bright red birds here are male scarlet taningers. The yellow birds are females. The tag on one bird is from 1887. Jerome McDonnell / WBEZ
shrinking birds
The Field Museum’s total bird collection has about half a million birds that date back to the middle of the 1800s. The bright red birds here are male scarlet taningers. The yellow birds are females. The tag on one bird is from 1887. Jerome McDonnell / WBEZ

What Dead Birds Can Tell Us About Climate Change

Over the past 40 years, ornithologist David Willard has added some 100,000 birds to the Field Museum of Natural History's extensive bird collection. Willard has collected, measured and preserved migratory birds that perished when they hit big buildings in Chicago. The buildings birds fly into include places like McCormick Place on the lakefront and high-rises downtown.

Willard, who is now collection manager emeritus at the Field Museum, has been collecting birds since 1978; in recent years he’s been getting help from volunteers with the Chicago Bird Collision Monitors. Each year, they rescue birds that hit downtown buildings and are hurt. But on those rescue missions, the volunteers also collect several thousand migrating birds that die after they hit buildings as they fly through Chicago. The volunteers deliver the dead birds to Willard at the Field Museum.

Willard’s is a unique collection for a number of reasons, including the wide variety of species and the fact that all the birds have been measured and weighed by one man with the same tools.

That consistency is one reason scholars at the University of Michigan were intrigued that Willard’s measurements showed the bill size of the most numerous bird in the collection — the white-throated sparrow — was getting smaller. They used Willard’s painstakingly collected data in a study that looks at connections between smaller body size in birds and increases in global temperatures. Think of it as a sparrow example of the ‘’canary in a mine shaft.”

“Our findings suggest that warming‐induced body size reduction is a general response to climate change,” according to the study. The Michigan scientists intend to continue their research into the links and implications of shrinking bird size and climate warming.

We thought you’d like to get a peak at Willard’s collection.

shrinking birds 1
Jerome McDonnell / WBEZ

When a bird comes in Willard weighs it, measures its wings, a leg bone and bill size. Because it’s a bit of a messy job, he writes down the information by hand in a ledger; the information is later logged into a computer.

shrinking birds 2
Jerome McDonnell / WBEZ

Some birds become study skins. Their insides are stuffed with cotton and they are preserved according to species in rows of chests.

shrinking birds 3
Jerome McDonnell / WBEZ

All these study skin birds get “toe tags.” The attached information includes the building they hit and the person who found them.

shrinking birds 4
Jerome McDonnell / WBEZ

Other specimens are skeletonized. Some by maggots in aquariums. The results look like this.

shrinking birds 5
Jerome McDonnell / WBEZ

The skeletons are transferred to boxes that again document the building where the bird perished and the person who found the bird.

shrinking birds 6
Jerome McDonnell / WBEZ

Jerome McDonnell covers the environment and climate for WBEZ. You can follow him @JeromeMcDonnell.