Gray-blue above with dark streaking on back; yellow underparts; dark streaking on flanks; white eye ring that is broken in the middle; white undertail coverts; white tail spots near the tips of the outer tail feathers; male has two indistinct whitish wing bars. 15 cm (5.75 in) in length. While sitting, this bird commonly pumps its tail, moving the tail downward quickly, then moving it back up.
The breeding season begins in late May and extends to early July. This species breeds in areas of young Jack Pines. The Jack Pine needs burning to help its seeds germinate, so areas maintained for this species require controlled burning to increase available nesting habitat. Both adults build the cup-shaped nest on the ground out of plant material and line it with fine grass and other material. The female lays 3-5 (usually 4-5) eggs that she incubates for 14-15 days. The male feeds the female while she is incubating. The young are altricial and fledge 12-13 days after hatching.
Kirtland's Warbler winters in areas with dense understories or scrub thickets. Except for singing males who perch on top of young Jack Pines, most of the activity of these birds takes place near or on the ground. The diet consists mostly of insects, which are taken by searching the pine needles, on leaves, and on the surface of the ground. This species is migratory.
The breeding distribution of the Kirtland's Warbler is limited to isolated areas in Michigan. The only known wintering areas are the Bahama Islands, although some other less reliable reports have placed them elsewhere. In Georgia, this species might be seen during migration.
The Kirtland's Warbler is Federally listed as an Endangered species. Fire supression programs have reduced the quality of the habitat for this warbler. Its decline has been attributed to habitat loss, habitat modification, and parasitism by the Brown-headed Cowbird. The Brown-headed Cowbird lays its eggs in other birds' nests, allowing the host parents to raise its young instead of or in addition to their own. Since the 1970s, cowbird removal programs have increased the reproductive ability of the Kirtland's Warbler.
The most similar species is the Prairie Warbler. The Prairie Warbler is smaller (12 cm), and it has face patterning that the Kirtland's Warbler lacks. The Palm Warbler is also similar, but it has bright yellow undertail coverts.