Incubation takes about 14 days. The nestlings develop rapidly and leave the nest by the ninth day. Both parents care for the brood, but some Kirtland's may initiate a second nest. In that case, the female incubates the second nest while the male cares for the first brood. By September, the chicks are strong enough to begin the annual migration to the Caribbean.
Plants associated with the bird's winter home are pine forests and broad-leafed scrub.
The warbler's specific nesting habitat requirements and other natural factors have limited the population to a small size. Because the warbler only nests in large stands of young jack pines created by dynamic forces, such as forest fires, any factors that curtail those forces may reduce the birds' reproductive success. Forest fire control measures have contributed to reduction of the bird's habitat. Fire suppression is necessary in Northern Michigan forest land management, especially to protect human life and property. But, fire control prevents the natural regeneration of jack pine because the heat of fire is necessary to open their cones and release their seeds.