BIRD OF THE WEEK: 5/8/2015
SCIENTIFIC NAME: Setophaga kirtlandii
POPULATION: 4,000 individuals
HABITAT: Dense stands of young jack pine
The yellow and gray Kirtland's Warbler has one of the smallest breeding ranges of any North American bird—almost the entire population breeds in north and central Michigan, with small numbers in Minnesota, Wisconsin, and Canada. These birds winter only in the Bahamas and the Turks and Caicos Islands.
Key threats are fire suppression, brood parasitism by Brown-headed Cowbirds, and loss of habitat on the wintering grounds. Poorly sited wind turbines are also a growing hazard, especially during migration.
Breeding Kirtland's Warblers need dense young stands of pines that are six to 15 years old and five to 20 feet high, where the warbler nests on the ground in an open cup of grass, sedges, pine needles, and leaves. These birds forage among the trees at low to mid-levels, eating insects, larvae, and small fruits like blueberries.
For optimal breeding success, Kirtland's Warblers require large areas — more than 160 acres — of dense young jack pine. This early-successional habitat was historically created by wildfire, but fire suppression programs almost eliminated it — and the species itself, which was one of the first to be listed under the Endangered Species Act soon after its passage in 1973. By 1987, numbers of Kirtland's Warblers had dropped to a low of 167 singing males.
Thanks to habitat management programs that include managed burns, clear-cutting, and seeding of jack pines — plus constant cowbird control — the number of singing males rebounded to over 2,000 pairs by 2012.
Keeping the Kirtland's Warbler population on the road to recovery will require continuing programs to create young jack pine forests and reduce nest parasitism by Brown-headed Cowbirds. Meanwhile, since the 1990s, a multi-agency monitoring program in the Bahamas has been conducting research to learn more about the bird's winter habitat.
ABC filed a formal petition with the U.S. Department of the Interior in February 2015 calling for more stringent regulations on wind energy projects, which will benefit not just Kirtland's, but other threatened migratory birds such as Cerulean and Bay-breasted Warblers, Golden Eagle, and Bicknell's Thrush.