Kirtland's warbler (Dendroica kirtlandii) was described in 1851 and the first nest was discovered in 1903 in northern lower Michigan [1]. Until 1996 all known nests were within 60 miles of this site [1].
Kirtland’s warblers nests in grasses and shrubs below living tree branches in jack pine forests that are five to ten years old [1]. This early seral stage habitat was historically maintained by fire [2]. The population size peaked between 1885 and 1900, probably due to the cessation of logging during a period of widespread fire [1]. By 1951, however, the warbler had been reduced to 432 pairs due to fire suppression and nest predation by brown-headed cowbirds [1, 3].
Between 1957 and 1962, the U.S. Forest Service and the Michigan Department of Natural Resources created four warbler management areas within state and national forests [1]. The population increased slightly to 502 pairs by 1961, but then declined to its lowest point of 201 pairs in 1971 [3]. By 1973, the Kirtland’s warbler management areas contained 53% of the nesting population [1].
During the mid 1970s, some 134,000 acres of jack pine forest in 24 units was designated fo Kirtland's warbler management on state and national forests. Additional lands were added through the 1990's to bring the total public land specifically managed for the Kirtland's warbler to more than 150,000 acres [1]. These forests are managed by logging, burning, seeding, and replanting on a rotational basis to consistently provide approximately 38,000 acres of productive nesting habitat [1]. In addition, in 1972 the U.S. Fish and Wildlife Service, in cooperation with the U.S. Forest Service, Michigan Department of Natural Resources, and the Michigan Audubon Society, initiated a program to control cowbirds which had been causing drastic declines in Kirtland’s warbler reproductive success [1]. An average of 4,000 cowbirds per year have been removed from Kirtland's warbler breeding areas [1].
The total population remained at about 200 pairs through 1989, began to increase in 1990, and grew steadily to a preliminary count of 1,701 territorial males 2007 [1, 2, 4, 5]. 1,679 of the 2007 territories were in Michigan, three in Wisconsin, and one in Ontario [5]. This marked the first reported nesting in Ontario since the 1940s [4] and the first ever reported in Wisconsin [5]. At least one of the Wisconsin territories was on Plum Creek Timber Company lands in the centeral part of the state [4].
Recent fires and continued management of habitat and cowbirds suggest that the population will continue to grow over the next decade or so.
[1] Michigan Department of Natural Resources. 2006. Kirtland's Warbler (Dendroica kirtlandii). Website <http://www.michigan.gov/dnr/0,1607,7-153-10370_12145_12202-32591--,00.html> accessed may, 2006.
[2] Michigan Department of Natural Resources. 2005. Michigan’s Kirtland’s Warblers Set New Record High for Census Count. Website <http://www.michigan.gov/dnr/0,1607,%207-153-10371_10402-122119--M_2005_7,00.html> accessed May, 2006.
[3] Olson, J. A. 2002. Special animal abstract for Dendroica kirtlandii (Kirtland's warbler). Michigan Natural Features Inventory, Lansing, MI. 5 pp.
[4] U.S. Fish and Wildlife Service. 2007. Discovery of rare bird nest is cause for celebration. Press release dated June 14, 2007, http://www.fws.gov/midwest/News/Release07-59.html
[5] Parham, G. 2007. Personal communication with Georgia Parham, U.S. Fish and Wildlife Service, August 21, 2007. |
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