By: Inas Essa

The seasons are changing with every passing year; winters have become colder, summer has been bringing unbearable heat waves, while the in-between has been almost lost. What lies behind that is climate change, which has been shaping our lives differently.

Away from humans, other creatures have been suffering from such change, which has been impacting species and ecosystems in destructive ways. A new study published in the Journal of Animal Ecology has indicated that climate change has caused birds to lay their eggs a month earlier than they did a century ago; an issue that cannot be overlooked.

Collecting Data from Museum Collections

In the recent study, researchers depended on hundred-year-old museum collections, which, when compared to today’s, show that birds are nesting earlier in the spring. They suggest that this shift is due to climate change.

The study mentions that, although spring has been the time for birds to start building their nests, many species are nesting and laying eggs about a month earlier than they did a century ago. They say that the shift in egg-laying—around 25 days—has happened in almost a third of the bird species nesting in Chicago.

"Egg collections are such a fascinating tool for us to learn about bird ecology over time," says John Bates, curator of birds at the Field Museum and the study's lead author. "I love the fact that this paper combines these older and modern datasets to look at these trends over about 120 years and help answer critical questions about how climate change is affecting birds."

The Study Trigger

What had triggered the study in Bates’ head was editing a book about eggs. "Once I got to know our egg collection, I got to thinking about how valuable that collection's data are, and how those data are not replicated in modern collections," he says.

In the museum, the egg collection occupies a small room with many cabinets, each containing hundreds of eggs, most of which were collected a century ago. They are stored in small boxes and labeled with the kind of bird they belong to, the origin, and when they were collected. "These early egg people were incredible natural historians, to do what they did. You really have to know the birds in order to go out and find the nests and do the collecting," says Bates. "They were very attuned to when the birds were starting to lay, and that leads to, in my opinion, very accurate dates for when the eggs were laid."

To make the compassion, researchers collected data about by recognizing 'nesty' behavior, which includes gathering nest material, like twigs, grass, roots, or bark, depending upon bird species. Moreover, they used mirrors mounted on long poles to closer look into high-up nests and kept close track of the dates when eggs were laid and hatched.

Early Nesting

The analyses have shown that: among the 72 species for which historical and modern data were available, about a third have been nesting earlier, as birds whose nesting habits changed were laying their first eggs about 25 days earlier than they were a hundred years ago.

Taken together, scientists attributed that to the climate change impact, which has dramatically affected many aspects of biology; such as the rising temperatures and the amount of carbon dioxide in the atmosphere.

Finally, they indicate that even though the temperature changes are not that high, these changes translate to different plants blooming and insects emerging; things that probably could affect the food available for birds.

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