Whooping Crane prospects
Why biologists believe that the number of endangered Whooping Cranes that breed in Canada and winter in Texas may not reach 1,000 birds, an important goal for the recovery of the species, for another half century.
Published: April 20, 2012
Whether we ever get to replace Endangered with Threatened as the official designation of the Whooping Crane is ultimately a question of numbers.
One goal to downlist the species, set in the official recovery plan published in 2007, is a minimum of 1,000 individuals in the population that breeds in Canada’s Wood Buffalo National Park and winters primarily at Aransas National Wildlife Refuge on the Texas coast.
Today the flock totals about 300 birds. This past winter, an exact count eluded biologists because several cranes stayed far north of Aransas. (For more about challenges facing Whoopers at Aransas, see Founding Editor Eldon Greij’s “Amazing Birds.”)
In the recovery plan, the U.S. Fish and Wildlife Service and Canadian Wildlife Service estimated the population could reach the 1,000-bird goal and be downlisted by 2035. A new analysis by independent biologists, however, casts doubt on whether the target can be reached at all. Karine Gil-Weir, a crane population ecologist at Nebraska’s Crane Trust, and colleagues at Texas A&M University say the population in 2035 may be around 715 birds.
The earliest it would reach 1,000 may be the mid-2060s — half a century from now.
Due to habitat limitations, it’s also possible that “a population of 1,000 may not be attainable and the population growth rate may slow markedly by 2035,” the researchers write in the Journal of Field Ornithology.
They made their prediction after studying the survival rates and breeding histories of 132 Whoopers that were banded at Wood Buffalo as juveniles from 1977 to 1988.
Gil-Weir’s paper was published in February, just after the U.S. Fish and Wildlife Service issued a new five-year assessment of the Whooping Crane’s status. However difficult the 1,000-bird goal may seem, it appears to be the most viable path to downlisting, the service concluded. That’s because to date all reintroduced flocks — in Idaho, Florida, and Wisconsin — have failed to establish self-sustaining populations.