Animals such as deer, turkey, and raccoons are wildlife generalists: they can exploit many different habitats to find the food, water, and cover they need to thrive. However, there are some animals that need very specific conditions to survive. The Kirtland’s warbler is an example of a bird that has very specific habitat requirements. Because of this, the warbler nearly became extinct in the 1960’s with only a limited number of breeding pairs found in a small section of Michigan.
The Kirtland’s warbler requires dense, young 80-400 acre Jack pine stands to fulfill its habitat requirements. Furthermore, the warbler does not extend as far north as Jack pine’s native range. These birds seem to prefer the southern range of the pine throughout Michigan, Wisconsin, and Southern Ontario. The warbler prefers young stands that are 4 – 20 years of age. This tiny songbird can fall prey to a number of predators, including the brown headed cowbird which exploits the nest of the warbler by laying its eggs in warbler nests. The young cowbird chicks usually outcompete the chicks of the smaller birds.
Given the restrictive habitat requirements and everything else that is stacked up against them, it is no wonder that Kirtland warbler numbers have declined. However, in 1976, a joint conservation effort was developed to save this bird from the brink of extinction. Most of the effort involved the planting of Jack pine forests and managing existing pine stands to develop the attributes that the warbler required. Most of this management involved creating young stands by cutting mature Jack pine stands and replanting or using controlled burning to develop young pine stands. There is also a program designed to trap cowbirds to lessen their impact on the warbler. When these programs began, scientists estimated that there were about 50 breeding pairs of the warbler found exclusively in the lower peninsula of Michigan. Now the range of the warbler has expanded so that it is found in both the upper and lower peninsula of Michigan, Wisconsin, and Southern Ontario. In addition, it is now estimated that there are 2,500 breeding pairs of the bird. This number is increasing, to the point that here is some thought of delisting the Kirtland’s warbler as a Threatened and Endangered species. Given these outcomes, it appears that the Kirtland’s warbler is truly a conservation success story.
Article by FCFCDB member
Nature Note for 1/12/20