Crawford County, Michigan
Note: This information is provided for reference purposes only. Although the information provided here was accurate and current when first created, it is now outdated.
Pesticide Table for Kirtland's Warbler | About Kirtland's Warbler
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Kirtland's Warbler (wood)
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|28||Do not apply within 100 yards of species habitat for aerial applications or within 20 yards of species habitat for ground applications.|
Kirtland's warbler [Dendroica kirtlandii]
Kirtland's warbler is a small song-bird, approximately 6 inches long. It has a blue-grey back and a yellow belly with dark spotting on the breast and sides. Male warbler's have a black cheek spot while the female spot is grey, but both sexes have a white eye ring that is broken by a dark eye line. It is unique from other blue-grey warblers because it wags or bobs its tail when it walks.
The warbler builds its nest on the ground amongst thickets of five- and six-year-old jack pines. Nests, constructed of bark, grass, pine needles and hair, contain three to five eggs that are white and speckled with brown. The habitat of this species is created and maintained by intense, periodic brushfires that prevent an area from being overgrown. In addition, Kirtland's warblers require Grayling sand, a porous soil that allows rainwater to quickly drain and prevents ground nests from becoming flooded. Greyling sand is found in 29 counties of the lower Michigan peninsula and corresponds to areas of naturally occuring jack pine stands.
The migration pattern of Kirtland's warbler is a direct route between nesting grounds in Michigan and its wintering range in the Bahamas and Dominion Republic with resting locations along the North and South Carolina coasts. The warbler's wintering grounds are low, broadleafed scrub, the dominant vegetation in the Bahamas and Dominion Republic.
Because of the limited habitat of Kirtland's warbler, its historic range is presumed to have been limited to Minnesota, Wisconsin, Michigan, and Ontario. Recent studies have indicated a few stray male warblers in Wisconsin and Minnesota but there is no evidence of nesting. Currently, all nesting sites are believed to be in Michigan, with approximately 90% located near the Au Sable River in Crawford and Oscoda counties. In 1951 approximately 1,000 songbirds were documented to be found in Michigan, but in 1989 researchers recorded only about 400 birds.
The decline of this species is attributed to loss of suitable habitat due to diminished size and frequency of fires in the Au Sable River watershed and the replacement of naturally occuring jack pines with introduced hardwoods. Diminished burns and the reduced jack pine stands has reduced suitable habitat from about 15,000 acres in the 50's and 60's to the current approximation of 4,500 acres. Also threatening warbler populations is parasitism by the brown-headed cowbird (Molothrus ater). The cowbird lays eggs in warbler nests which hatch before warbler chicks, outgrowing and outcompeting them for food. In the 1970's cowbirds reduced warbler egg production by approximately 40% and nearly wiped out their reproductive efforts. This lead to the relocation of nearly 40,000 cowbirds by the 1980's.
The Michigan Department of Natural Resources currently administers 25.4 acres of land that is carefully managed to attract nesting warblers. In addition, the U.S. Forest Service administers more than 4,000 acres in the Huron National Forest in Oscoda County that is ideal habitat for the warbler.
Matthews, J.R. (ed.), The Official World Wildlife Fund Guide to Endangered Species Vol.II, Beacham Publishing Inc, Washington, DC. pp. 601-602.