In early June, the squabbling on Breeding Island begins in earnest as those strutting high-strung stars of the tropics, the Caribbean flamingos, lay fist-size eggs. On many mornings, National Zoo biologist Sara Hallager walks out to the island, a muddy mix of dirt and peat moss surrounded by a ring of water, to dupe the birds in the name of science.
She slips off her shoes for better traction, slaps on a pair of rubber gloves and inches toward the mini-moat as the birds raucously express their alarm. "I've never been bitten on the face, but it's not for their lack of trying," Hallager says. Some birds cooperate and stand right up. She has to lift others bodily. Then she pulls the switcheroo.
It has long been standard practice for Zoo biologists tending captive bird colonies to substitute fake eggs for real ones, which are then placed in an incubator for safekeeping until they're ready to hatch. But nowadays some of the dummy eggs aren't so dumb. They are, in fact, sophisticated electronic devices that monitor such variables as temperature and rotation and send the data to a computer. The Zoo's four eggs, at $6,500 apiece, are designed to answer a basic question: What exactly goes on under a roosting bird? "Right now we're doing a lot of guesswork," says Hallager, who specializes in flamingos and kori bustards, large birds native to the African savanna. "But this data will help us mimic natural incubation as closely as possible."
In one recent test, the researchers found that a kori bustard frequently turned its egg and moved on and off it throughout the night, with temperatures under the bird fluctuating by as much as 20 degrees. Such findings may lead Zoo staffers to turn incubated eggs more often and vary the temperature. The Zoo has had success hatching kori bustards—it's one of the few facilities in the world to breed the birds—but there's always room to improve, Hallager says: "By learning how Mom's doing it, we can pretty much nail it down."
The telemetric egg was originally developed in 1998 by Advanced Telemetry Systems, a Minnesota-based company, to help the St. Louis Zoo thwart wild raccoons that were stealing waterfowl eggs. Zoo biologists were eager to get the real eggs into incubators as soon as possible, and the telemetric eggs helped them decide how best to care for the eggs once they did. Another facility using the device is the Calgary Zoo in Alberta, Canada, which is hoping to boost its success breeding whooping cranes. Researchers there have found that the nests of roosting cranes are both cooler and drier than they'd thought, and they've purchased new incubators that more closely mimic those conditions.
National Zoo biologists hope that such findings, combined with their own telemetric egg data, will yield a greater understanding of bird reproduction. The Zoo says there's a critical need to add to the 65 kori bustards in U.S. facililties, including the eight at the Zoo. The birds are declining in number in their native habitat even as biologists are increasingly wary of taking birds from the wild to sustain captive populations. "What we have in this country is all we have, so the more we learn how to breed them, the better," Hallager says.
As for the roosting Caribbean flamingos, they typically spend only about 25 days atop a dummy egg before Hallager returns to Breeding Island to make another swap. This time as she approaches, the birds are even more riled to see her. She goes to a nest, grabs a dummy egg and delicately replaces it with one that's on the verge of hatching. Mom knows it's the real thing when she hears peeping.