Smithsonian Migratory Bird Center scientists track Kirtland's warblers using light-level geolocators to reveal their migration routes and full wintering distribution. The Kirtland's warbler is an endangered migratory songbird that breeds almost exclusively in Michigan, with a few isolated populations in Wisconsin and Ontario. They winter primarily in the Bahamas, with some individuals wintering in Turks and Caicos and Cuba. Kirtland’s warblers nest on the ground and will only breed in young (5- to 20-year-old) Jack Pine forests.
Decades of fire suppression prevented the creation of new breeding habitat and intense nest parasitism by brown-headed cowbirds limited reproductive success. These two factors led to population declines and, as a result, they were among the first group of species to be declared endangered in 1967. Despite a successful cowbird control program that began in 1971, the population dropped to just 187 males in the wild in 1974 and again in 1987.
Subsequent planting of new Jack Pine habitat by state and federal agencies has led to substantial recovery of the population. Kirtland’s warblers represent a great success story for the Endangered Species Act, and more than 2,300 males were counted in the last population census. However, despite these conservation successes, they remain one of the most rare and range-restricted songbirds in North America.
SMBC's Kirtland's warbler research program has three main components:
- First, researchers are investigating how to change the cowbird control program to reduce costs and conservation-reliance of Kirtland's warblers.
- Second, SMBC collaborates with the Cornell Lab of Ornithology and eBird to incentivize citizen scientists to pinpoint the locations of stopover sites used by Kirtland's warblers during migration.
- Finally, researchers use coded radio tags and a network of automated telemetry towers in Florida, Ohio and Michigan to study individuals in the Bahamas, track them through migration and pinpoint their breeding locations.
This innovative approach will allow researchers to estimate spring migration survival and more directly estimate carry-over effects from winter to breeding. Together, these three research components will help provide the conservation community with the information needed to ensure that Kirtland’s warblers persist for generations to come.