These 100-year-old eggs at the Field Museum shed new light on climate change | Chicago News

The Field Museum’s collection of historic eggs sheds new light on climate change. (Patty Wetli / WTTW News)

A new study by the Field Museum shows that climate change is disrupting when birds lay their eggs.

This latest research, published in the Journal of Animal Ecology, used historical nesting information available in the field and compared it to data collected between 1990 and 2015 by ecologists working for Morton Arboretum.

The resulting analysis found that about a third of the 72 species studied lay their first eggs an average of 25.1 days earlier than 100 years ago.


The team obtained long-term data on carbon dioxide levels in the atmosphere, which correspond to trends in temperature, and found that they were correlated with changes in egg-laying dates.

On the one hand, the study’s findings could be seen as positive, as they demonstrate the adaptability of birds to climate change, said John Bates, curator of birds at the Field Museum and lead author of the study. .

But the complexity of bird biology and behavior, and their relationship to other organisms within a larger ecosystem, raises all sorts of questions about whether early nesting makes them more or less vulnerable to climate change. , did he declare.

Are the insects these birds depend on for food or the plants they need for their habitat adapting at the same rate? How will this affect competition for resources? Bates predicts that the spawning data will spawn idea after idea for other researchers to study.

“There are all sorts of really important nuances that we need to be aware of in terms of how animals react to climate change,” he said.

Since the study is focused on northeast Illinois, he also wants colleagues across the country to replicate the process to see if they observe similar changes.

Egg collecting was all the rage 100 years ago, but today collections like those at the Field Museum are rare.  (Patty Wetli / WTTW News)Egg collecting was all the rage 100 years ago, but today collections like those at the Field Museum are rare. (Patty Wetli / WTTW News)

This latest revelation about the impact of climate change was made possible by a hobby that is out of fashion: egg collection.

Much of the Field’s cache of eggs – tens of thousands, hidden in drawers, resting on cotton pillows – date back to the golden age of collecting in the late 19th and early 20th century, when it was fashionable. Eventually, legal restrictions, namely the Migratory Bird Treaty Act of 1918, virtually ended the practice.

The ethics of egg collection pose a “yes, but” dilemma for scientists, Bates said.

“Yes, they were viable birds. Collecting anything obviously has deadly implications. But we can do a lot with this data,” he said.

The fact is that for a long time no one paid attention to egg drives, including Bates.

Many museums and private collectors have lost their samples, and much of what remains is gathering dust or locked away out of sight.

Bates took an interest in Field’s collection, housed in a space roughly the size of a bungalow belt kitchen, while editing “The egg book“, a coffee table reference tome featuring the eggs of the field, written by the biologist Marc Hauber.

Bates was struck by the fact that the roughly 5 million eggs still found in collections from places like the Field were a neglected resource.

“We have this massive dataset, each specimen is a data point. And people ignore that data,” he said.

For the purpose of egg-laying study, the value of Field’s collection lies as much in the detailed notes accompanying each specimen as in the eggs themselves. The tags specify the type of bird, the location of the nest and the date of collection. Because eggshells are easiest to store right after they’ve been laid, before any incubation, the date of collection is a fairly accurate proxy for the date of lay, according to Bates.

The trickiest part was finding modern nesting data for comparison, given the lack of collection that has occurred since the 1920s.

Bates turned to field colleague Bill Strausberger and Chris Whelan, an evolutionary ecologist at UIC, for help. The two men had worked on separate projects at Morton’s Arboretum that involved locating nests, monitoring them, and recording egg laying and hatching. (All the eggs remained in their nests.)

It is impossible for Bates to overstate the chance of having access to this kind of information.

“What Chris and Bill did was so unusual,” he said.

Their datasets, which spanned the past 25 to 30 years, contained Field’s own information. This left a gap in the mid-twentieth century, which Mason Fidino, a quantitative ecologist at Lincoln Park Zoo, filled with a data model.

So what other secrets could the Eggs of the Field reveal?

Bates said researchers are just beginning to realize the potential of such collections. Do the physical characteristics of the eggs, such as shape and size, change? And if so, for what purpose? What about their chemical composition? Has it evolved over time or has it remained static?

“That’s why these collections are important,” he said, but only if they are used. “If they’re just sitting here, we’re not doing our job.”

Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]

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