Birds Are Laying Eggs Earlier Likely Due to Climate Change

It’s an annual harbinger of spring: Birds singing, building nests, and laying eggs. But the timetable has been gradually changing. A new study finds that many bird species are building their nests and laying eggs nearly a month earlier than they did a century ago. Researchers compared bird egg information from museum collections with recent bird behavior observations and found that about one-third of the bird species that nest in Chicago have moved their egg-laying to an average of about 25 day

"The findings are important because changes in climate that drive changes in the timing of ecological events (a phenomenon known as phenology) can lead to disruptions in things like the emergence of leaves of trees and the insect herbivores that feed on those leaves, which may lead to 'mismatches' with the timing of birds, whose young depend on parents foraging for those insects to provide food for the developing young," Whelan says. "If the timing of such events becomes highly mismatched, parent birds may lose the ability to adequately provision their offspring with food, leading to offspring death and reproductive failure. Luckily, we have not yet documented such mismatches in our study area." Bates points out that breeding bird data over the last 40 years has found that many North American bird species have had significant drops in population. Researchers want to know why this is happening.