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

"What most surprised me was that many long-distance migrant species were among those showing a change in timing. This was surprising because the timing of their migration is linked more to changes in relative hours of daylight than to changes in temperature or other climate-related factors," Whelan says. "The change in timing is still possible, however, because they tend to arrive on the breeding grounds with 'time to spare,' so to speak. Once here, they seem to adjust based on prevailing climatic conditions, which have slowly been changing over the course of our study, from the 1870s to modern times."