Say what you will about Victorian egg collectors, but it’s hard to deny that they were a dedicated lot. Charles Bendire, a 19th-century ornithologist and U.S. army major, once braved enemy fire to snag a rare bird egg from a tree, cushioning it in his mouth while he scrambled down to safety; upon finding that the egg was stuck in his mouth, he had his men remove one of his teeth to free it. Another egg enthusiast, Frances J. Britwell, was strangled to death by his climbing rope while trying to reach a nest in a tall pine tree on his honeymoon. Egg collecting was considered a hobby for gentlemen, but it was not for the faint of heart.

Today, the fruits of these collectors’ tree-shimmying, egg-swallowing labor can be found in museum collections around the country: Shiny green clutches laid by South American tinamous; nondescript speckled eggs deposited in other birds’ nests by cowbirds; the occasional massive, melon-sized elephant bird egg; all tucked away in floor-to-ceiling drawers.

“The scientific value of the collection and the accompanying manuscripts is immense,” says Douglas Russell, the senior curator of birds’ eggs and nests at the London Natural History Museum. “We have inquiries and researchers visiting the collection from all over the world,” working on projects “from historical research on breeding distribution to ground-breaking research to unveil the biology of eggs and explain the diversity in eggshell coloration, patterning, and shell-structure across birds.”

The handwritten notes that often accompany the eggs can be as valuable to curators as the eggs themselves. “Egg collections are some of the first ones where people took really good natural-history data,” says John Bates, the associate curator of birds at Chicago’s Field Museum (where I work). “They had to feel confident that they were getting the right species, so they took really detailed notes about historical habitats, down to stuff like, ‘Found clutch two feet off the ground in a willow,’ with specific information about where the eggs were found, down to street names.”

These precise details have helped scientists understand the changes in bird nesting behavior in the past century, Bates adds. For example, “the nest slips that were written down when some of our eggs were collected a hundred years ago show that birds are starting to nest earlier in the year than they used to. It’s a piece of the whole picture of human-driven climate change.”

In some cases, these historical eggs have also played a role in major scientific discoveries. The banning of the pesticide DDT, for example, relied on research conducted on several museum egg collections—scientists were able to compare turn-of-the century eggs to modern ones to show the link between the pesticide and the brittle, prematurely cracked eggshells that spelled disaster for birds of prey, including the bald eagle.

Egg collecting is now illegal for citizen scientists in the vein of Bendire and Britwell, but real scientists can get permits. However, few do, in part because the process is so labor-intensive.

“For egg collecting, there’s a very brief window of time, and it’s a very time-consuming activity—you have to watch the birds and follow them to know where their nests are,” said Paul Sweet, the collection manager of birds at the American Museum of Natural History. “I’ve done a lot of collecting, but I’ve never collected an egg—it’s just not something that a lot of people do.” Sweet’s colleague Tom Trombone, the bird collection’s data manager, knows the number of eggs the museum has—17,921—off the top of his head, in part because it’s a number that hasn’t changed in years.

But while egg collecting has fallen out of favor in recent years, scientists are divided on whether the practice should be resurrected. Some ornithologists argue that with the millions of eggs already in museum collections, we’ve got all the information we need. “We rarely collect eggs these days,” Russell notes, “but if it was considered scientifically important, for example to detect major trends of conservation concern and was both ethically and legally possible, then we would collect.”

Others are more enthusiastically in favor of a return to the practice. “By not collecting eggs today, we might be missing valuable information,” Bates muses. “Victorian egg collectors never dreamed of how their eggs would be used in the future.”