What a lark: bird collections reflect air pollution

Birds lodged at museums for more than a century are providing insights to soot levels in America’s industrial heartland. Jeff Glorfeld reports.

Horned Larks from The Field Museum's collections, with grey birds from the turn of the century and cleaner birds from more recent years when there was less soot in the atmosphere. Credit: (c) Carl Fuldner and Shane Dubay, The University of Chicago and the Field Museum