|A whooping crane pair forage with their chicks in Wisconsin. The endangered birds are getting better at nesting but chick survival is a problem.|
|Credit: Richard Urbanek|
Despite Chick Deaths, Guarded Optimism for Whooping Cranes
What’s killing whooping crane chicks at Necedah National Wildlife Refuge in Wisconsin? That’s not yet clear, but wildlife experts are on the case. Meanwhile, they’re advising wildlife enthusiasts to take the long view on prospects for the endangered species. The Wisconsin flock of giant, captive-bred birds is growing, albeit slowly, and now numbers nearly 100. And the adult cranes, evidence shows, are getting better at nesting — critical to species recovery.
“They’re doing exactly what we would predict — adapting, getting better at nesting and hatching chicks,” says Rich King, supervisory biologist at the refuge. “With a long-lived, slow-maturing species like this, recovery just takes a lot of time.”
Five of seven chicks hatched this year at the refuge died. That 71 percent mortality rate is consistent with the rate for past years, says King. But refuge biologists are now studying why survivability isn’t higher and if they can raise it. For the first time, they have forensic evidence that may help: the body of a dead chick. Generally, a chick is presumed dead if it’s missing from a nest that has a second chick or if its parents are no longer seen feeding or tending it. Until now, no dead chick has ever been recovered.
Experts who examined the dead chick found no obvious cause of death such as starvation or predation. Further tests will culture blood and tissue for possible bacteria or viruses. Meanwhile, the refuge and its partners — the Wisconsin Department of Natural Resources (DNR) and a nonprofit group called Operation Migration — have stepped up chick surveillance, conducting four daily overflights of the youngest chicks and three daily overflights of chicks three and four weeks old.
King, meanwhile, is cautiously optimistic. Wisconsin has reintroduced several species, he says, and each went through a slow initial phase before succeeding. He cites two examples: wild turkeys and trumpeter swans. Between 1952 and 1956, biologists brought in 700 turkeys from game farms in Pennsylvania. The population struggled until biologists added wild-caught turkeys from Missouri. “Now just about every place in Wisconsin has wild turkeys,” says King. “But it took 20 years for those birds to reach critical mass.”
In the 1990s, the U.S. Fish and Wildlife Service and Wisconsin DNR teamed up to reintroduce trumpeter swans, bringing in swan eggs from Alaska. “It wasn’t until 2000 that the population took off,” says King.
Compared to turkeys and swans, whooping cranes nest later (at age three, four or older) and produce fewer chicks. Of the two eggs they usually lay, rarely does more than one survive. “If a snapping turtle gets a chick, well then, they’re done,” says King. “You’ve got to wait another year. It’s painfully slow to get to critical mass because their productivity is so extremely low.”
The whooping cranes that summer in Wisconsin and winter in Florida belong to one of three crane populations in the country that the Service is working to recover. In the 1940s, the world’s total population of whooping cranes was about 16.