The Remarkable Recovery of the Kirtland's Warbler
By Chris Mensing
East Lansing ES Field Office
ESA at 40 story : To commemorate the 40th anniversary of the Endangered Species Act, the U.S. Fish and Wildlife Service is issuing articles that highlight endangered species conservation in each state. This month's article focuses on Michigan. More about the Endangered Species Act 40th anniversary and other endangered species conservation articles can be found at http://www.fws.gov/endangered/ESA40/index.html
Forty years ago, the Kirtland's warbler was on the brink of extinction. Today, this lively songbird of northern Michigan's jack pine forests is the subject of a great recovery story -- rebounding from a low of 167 males in 1987 to a record-breaking 2,090 in 2012.
The Kirtland's warbler was among the first animals to gain federal protection in 1967 under the Endangered Species Preservation Act, a precursor to the Endangered Species Act. After the species was listed as endangered, biologists from the U.S. Fish and Wildlife Service, Michigan Department of Natural Resources, U.S. Forest Service, and other conservation organizations met to discuss the threats and determine what actions were necessary to recover the species to the point where Endangered Species Act protection was no longer necessary for its survival. In 1974, this group completed the first-ever recovery plan under the act, which identified habitat loss and brown-headed cowbird nest parasitism as the primary threats to the species.
To address habitat loss, the U.S. Forest Service and Michigan Department of Natural Resources initiated a program of jack pine management across the glacial outwash plains of Michigan's northern lower peninsula. Kirtland's warblers nest in young jack pine trees, but years of fire suppression had allowed the jack pine forests to become too old for the birds to use. To recreate this nesting habitat, foresters began planting and managing large stands of dense jack pine to mimic the effects of wildfire. Over 210,000 acres are designated as Kirtland's Warbler Management Areas and managed on a 50-year rotation, allowing jack pine to grow to commercial size before being cut and replanted.
"The Kirtland's Warbler Management Areas provide nearly 40,000 acres of jack pine habitat suitable for Kirtland's warbler nesting each year," said Christie Deloria, biologist in the Service's East Lansing Field Office. "They also support many other species, including snowshoe hare, wild turkey, spruce grouse, white-tailed deer, eastern bluebird, and upland sandpiper."
Another critical recovery tool for the Kirtland's warbler is a brown-headed cowbird trapping program. The brown-headed cowbird is a nest parasite that knocks Kirtland's warbler eggs out of the nest and replaces them with their own. Kirtland's warblers then unknowingly raise the cowbird's young. Removing cowbirds during the warbler's breeding season reduces the pressure of nest parasitism and increases the warbler's nesting success.
Even with these efforts, the Kirtland's warbler population declined to an all-time low in 1987, restricted to just 22 townships in northern Michigan. Through research and monitoring, the Service, USFS, and MDNR refined management techniques. Over the last 25 years, the population has increased to over 2,000 males in 2012, and has expanded to parts of Michigan's Upper Peninsula, Wisconsin, and Ontario.
Research and management continue across the warbler's breeding range and in the Bahamas, where the bird spends the winter. The Kirtland's Warbler Recovery Team remains an integral part of these efforts by facilitating coordination among the Service, USFS, MDNR, and many other individuals and organizations committed to recovering the species.
With the population nearing twice the recovery goal of 1,000 pairs, the challenge now is securing future jack pine management to promote recovery—the species' long-term conservation needs must be met before the species can be removed from ESA protection. The Service, with support from USFS, MDNR, the National Fish and Wildlife Foundation, and Huron Pines, is on an initiative that will address this recovery requirement.