A comparison of Horned Larks collected inside and outside of industrial areas during the early twentieth century. The specimens on the left were collected in Illinois, inside the U.S. Manufacturing Belt. The specimens on the right were collected along the western coast of North America, away from industry.
Birds Once Turned Black From Pollution—What That Teaches Us Today
Birds that flew over the U.S. Rust Belt during the 20th century have become a record for changing air quality.
It's a striking image—two rows of birds lined up side-by-side, one with white bellies, and the other nearly entirely black.
The birds are the same species of horned lark, a naturally white bird with a yellow chin, and have become part of an unconventional record of air pollution in the U.S. Rust Belt over the past 135 years.
Looking at more than 1,300 birds from five species that flew over the Rust Belt and were contained in natural history collections, two graduate students—Shane DuBay and Carl Fuldner from the University of Chicago—were able to tell how much black carbon, also known as soot, accumulated in bird feathers during the year it was collected. While the bird species have noticeable differences in color,