A new study published in the Journal of Animal Ecology has found that several bird species had nested and laid their eggs about a month earlier than they did 100 years ago.
By comparing recent sightings with centuries-old eggs kept in the museum’s collection, scientists have been able to determine that nearly a third of birds in Chicago laid eggs ahead by an average of 25 days. Researchers blame this to climate change.
Scientists have yet to find clear features shared by these species, such as size or migratory location, which could explain why they are changing their schedules.
“The majority of the birds we looked at eat insects, and insects’ seasonal behaviour is also affected by climate,” said lead author John Bates, curator of the bird division at the Field Museum in Chicago.
How animal and plant life cycles are affected by climate change and seasonal disruptions is a question that’s “becoming more front and centre in people’s minds,” Bates said.
The research also shows that the change in egg-laying corresponds with climate change. More research is needed, but Bates says one crucial thing is clear, “Climate change is happening, and also that we can do something about it.”
Scientists believe these changes may be one of the reasons for the sharp decline in bird species since the 1970s, with the United States and Canada losing about a third of their birds to about 3 billion birds, according to a 2019 study.
Bates and colleagues have studied the records of more than 1,500 egg shells preserved in the Chicago Field Museum, many of them between 1872 and 1920, when egg collection was a popular pastime. These Victorian-era egg enthusiasts list detailed handwritten labels, such as bird species and collection dates.
The scientists then compared those records with more than 3,000 modern records, including data describing the levels of carbon dioxide in the habitat from time to time for analysis.