Date of this Version
The 1971 census of the Kirtland’s Warbler taken on the warblers nesting grounds in North Central Michigan revealed that the population of this species had dropped to an all-time low of 201 singing males, as compared to 502 in 1961, a drop of some 60 percent in ten years. Breeding birds, furthermore, once found nesting in as many as nine counties during one nesting season returned to nest in only five counties in 1972, at which time the census indicated that the warbler population was remaining temporarily stable at approximately 200 singing males. Since the sex ratio of this species is thought to be 50-50, these data indicate that the total population of the Kirtland’s Warbler in the spring of 1972 was in the neighborhood of 400 individuals. The precipitous decline in the warbler population occurred despite the efforts of the U.S. Forest Service and the Michigan Department of Natural Resources to increase or at least stabilize the Kirtland’s Warbler population by manipulating, through control-burning and cutting, the jack pine habitat in which the warbler nests exclusively.