B
irds in the Upper Midwest are nesting and laying eggs nearly a month earlier than they did 100 years ago, and scientists say warming temperatures may be to blame.
In a new study published in the Journal of Animal Ecology on March 24, scientists found that the egg-laying dates for 72 species of birds in the Chicago area have shifted by an average of 25.1 days since the early 1900s and late 1800s. The shift was smaller for resident species but larger for short- and long-range migratory birds.
The researchers analyzed eggs in Chicago’s Field Museum, which hosts a vast collection of more than 50,000 hollowed-out eggs dating back from the 1870s to the 1920s, according to the Associated Press. The Field also holds information about which species laid the eggs and when they were collected. Like most eggshell collections, the number of specimens drops off after the 1920s ...
