Kirtland's Warbler Overview, All About Birds, Cornell Lab of Ornithology

The Kirtland's Warbler requires areas with small jack pines for nesting. The jack pine requires fire to open its cones and spread its seeds. The warbler first appears in an area about six years after a fire when the new growth is dense and is about 1.5 to 2.0 meters (5.0-6.5 feet) high. After about 15 years, when the trees are 3.0 to 5.0 meters (10.0 to 16.5 feet) high, the warbler leaves the area.

The female Kirtland's Warbler is more selective than the male in her choice of habitat, and the best areas attract more females than males. The last residents of a tract that is getting too old are always unmated males.