Kirtland’s Warbler Returns to its Wisconsin Birthplace
A Kirtland’s warbler that hatched and was banded in Wisconsin last year has returned to its birthplace in Adams County, providing a significant milestone in efforts to help boost populations of this federally endangered songbird.
“This is the first time we’ve been able to document that a bird hatched in Adams County has returned to the area,” says Kim Grveles, a Wisconsin Department of Natural Resources avian ecologist. It’s a very encouraging sign that Wisconsin is providing suitable and successful breeding habitat for these birds.”
Chris Mensing, endangered species biologist with the U.S. Fish and Wildlife Service, also hailed the news. “With endangered species, you never want to put all your eggs in one basket. Having a successful breeding population outside the core Kirtland's warbler range in Michigan helps protect the species from catastrophic events.”
Starting in the late 1990s, the protections and efforts made under the Endangered Species Act enabled the Kirtland’s warbler to start expanding its breeding territory to Wisconsin, Michigan's Upper Peninsula and Ontario.
Almost 200,000 acres of jack pine forest are currently managed as breeding habitat for this species, with the vast majority of land managed by the U.S. Forest Service and the Michigan Department of Natural Resources. Seney National Wildlife Refuge manages the 6,700-acre Kirtland’s Warbler Wildlife Management Area providing landscape features less common elsewhere.
Because the bird historically nested in young jack pine forests that were naturally regenerated by fire, “the land must be actively and intensively managed in the era of widespread fire suppression and less utilization of prescribed fire,” says Seney Refuge forester Greg Corace. Each year, Corace clear cuts tens to hundreds of acres of mature (30-60 year old) jack pine trees. Two-year-old jack pine seedlings are then planted in very densely-packed trenches by the Michigan Department of Natural Resources to roughly emulate restocking patterns that would result from wildfire. Typically, about five years later, the warblers move in. “But in 20 years,” says Corace, “after the trees have grown a bit, the birds are leaving, so we better have another stand ready somewhere else.”
Cowbirds lay their eggs in the nests of songbirds including Kirtland’s warblers. The warblers are unable to recognize cowbird eggs or chicks as different from their own young. Cowbirds hatch earlier, are larger, and more aggressive at begging for food than warbler chicks, which results in the Kirtland’s warbler parents raising a cowbird or two at the peril of their own brood.
The partners also are working to maintain and expand the mix of 5- to 20-year-old jack pine trees and barrens necessary by planting the tree species. Historically, such habitat depended on fire, Grveles says.
The returning bird was discovered in Adams County on June 3, 2013, by nest monitors Valarie Michel and Daryl Christensen. The bird had been hatched at the same site in 2012 and was captured and banded in August 2012 by Ron Refsnider and Joel Trick, both retired from the U.S. Fish and Wildlife Service. Refsnider estimates the chances of finding this individual at the same site a year after hatching was less than 15 percent.
Current and past reports on the Kirtland’s warbler