Did your backyard nest produce little songbirds a bit earlier this year?
A 120-year-old collection of eggshells held by Chicago’s Field Museum helped hatch an investigation by a national group of researchers. The museum houses hundreds of the shells, most of which were collected before the 1920s, along with data about the types of birds and when the eggs were laid. The scientists also used records of bird nesting observations taken in the Chicago area between 1880 and 1920 and about 1990 to 2015.
Over time, the researchers found, the average egg-laying date moved up for a variety of species in Chicago. Overall, the birds’ lay dates advanced by an average of 25.1 days, with less shift for resident species and a wider shift for short- and long-distance migrants.
The animals studied aren’t just early birds: They are sensitive to climactic shifts. The researchers found that small changes in temperature — approximated using carbon-dioxide data from over the years — affected birds’ laying patterns.
Climate change has shifted seasonal rhythms of animals and plants, which affects everything from bird food to bird habitats and can place birds in competition with one another for insects and other food sources. The earlier and warmer springs that accompany human-caused climate change can effectively strand birds that are born earlier than their traditional food sources.
The study points not just to the urgency of human-caused climate change but also the value of historic observations to modern scientists.
Combining archival data with modern observations, the researchers write, “will provide the ability to track, understand and perhaps even predict responses to present and future human-driven environmental change.”