Michigan's Kirtland's Warbler Population Continues to Grow

September 5, 2007 -- Michigan Department of Natural Resources officials today released annual survey information indicating the state's population of the endangered Kirtland's warbler continues to increase.

Biologists, researchers and volunteers in Michigan observed 1,697 singing males during the official 2007 survey period, up from 1,478 males observed in 2006. The 2007 population represents the largest number of singing males recorded since monitoring began in 1951. The lowest numbers were recorded in 1974 and 1987, when only 167 singing males were found.

The Kirtland's warbler survey is conducted each year over a 10-day period during the first two weeks of June when the birds are establishing their nesting territories. Warblers are detected by listening for their songs. The songs can be heard at distances up to one-quarter mile, providing an excellent way to detect the birds with minimum disturbance. Only the males sing, so estimates of breeding population size are obtained by doubling the number of singing males recorded, based on the assumption that each male has a mate in its territory.

The 2007 survey was a joint effort by the DNR, U.S. Forest Service, U.S. Fish and Wildlife Service, Michigan Department of Military Affairs and citizen volunteers.

This year, singing males (numbers in parentheses) were found in 12 northern Lower Peninsula counties: Alcona (175), Clare (147), Crawford (290), Grand Traverse (1), Iosco (238), Kalkaska (4), Montmorency (14), Ogemaw (529), Oscoda (198), Otsego (43), Presque Isle (6), and Roscommon (20). Surveyors identified 32 singing males in five Upper Peninsula counties: Baraga (1), Chippewa (8), Delta (7), Marquette (8), and Schoolcraft (8).

In the U.P., females were observed with the males, indicating nesting activity. Ten additional singing males were observed outside Michigan in Wisconsin (8) and Ontario (2). Of particular importance this year was the discovery of three Kirtland's warbler nests in Wisconsin, which represented the first documented breeding of Kirtland's warblers outside Michigan in many decades.

Although Kirtland's warblers have begun to expand into new areas, the core of the Kirtland's warbler population remains dependent on northern Michigan's jack pine barrens ecosystem for nesting habitat. The warblers nest on the ground and typically select nesting sites in stands of jack pine between four and 20 years old. Historically, these stands of young jack pine were created by natural wildfires that frequently swept through northern Michigan. Modern fire suppression programs altered this natural process, reducing Kirtland's warbler habitat. The result was that the population of Kirtland's warblers declined to the point that they were listed as endangered.

To mimic the effects of wildfire and ensure the future of this species, the DNR and its partners at the state and federal level manage the forests through a combination of clearcutting, burning, seeding and replanting to promote warbler habitat. Approximately 3,000 acres of jack pine trees are planted or seeded annually on state and federal lands, primarily for the purpose of providing habitat for Kirtland's warblers.

"New habitats are continually developed to replace those that become too old for Kirtland's warbler nesting," said DNR Endangered Species Coordinator Todd Hogrefe. "Through continuing management, we expect there to be sufficient habitat to support the warbler population through the foreseeable future."

Elaine Carlson, DNR wildlife biologist, emphasized how the habitat management program has produced benefits that extend well beyond the recovery of a single species. "In addition to generating habitat for the Kirtland's warbler, the jack pine management program provides valuable forest products as well as habitat for a variety of plants, songbirds, game animals and other wildlife," Carlson said.

For more information on the Kirtland's warbler, contact the DNR Wildlife Division, Natural Heritage Program, Box 30180, Lansing, MI 48909, or visit the DNR Web site: www.michigan.gov/dnr.

Source: Michigan Department of Natural Resources

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