This pine specialist breeds from mountains of the southwestern United States to the Caribbean coast of northern Nicaragua. One of the smallest warblers, it is an active forager, hopping and flitting rapidly among the outer foliage of high branches, perching on twigs and needles in search of insects and spiders, and occasionally fly-catching or hovering to obtain its prey. Northernmost populations, from northern Mexico and the United States, are migratory, whereas populations from central Mexico south to Nicaragua are only partially migratory or resident. The species prefers parklike stands of mature pines, a habitat that has declined over time through forestry practices of logging and fire suppression, at least in the northern parts of its range. Little is known about Mexican and Central American breeding populations.
Distribution and habits make Grace's Warbler one of the least known North American passerines. Its territories tend to be large, its nests well hidden, and individuals a challenge to follow. No comprehensive studies exist, and much basic information is lacking. Few nests have been found, few individuals have been collected or measured, and no studies have thoroughly documented basic information such as molt, migration, or population dynamics. Only 59 individual Grace's Warblers have ever been banded, far fewer than any other North American wood-warbler.
Its ecology has been studied mainly as a member of the bird community inhabiting pine or pine-oak forests in Arizona (Marshall 1957, Balda 1969, Szaro and Balda 1979, Brawn et al. 1987, Block et al. 1992, Rosenstock 1996, Block and Finch 1997, P. Beier unpubl.), Mexico (Marshall 1957; Block et al. 1992; Nocedal 1994a, 1994b, 1995), and Nicaragua (Howell 1971, 1972). These studies have documented the range of habitats occupied, microhabitats used for foraging, and densities of some populations. The only studies to date solely on Grace's Warbler focused on the singing behavior of individuals in northern Arizona (Staicer 1989), geographic variation in songs of the northern subspecies (CAS), and nesting behavior of a few pairs in southwestern Colorado (S. Hutchings unpubl.).
This account compiles information from the studies mentioned above, from various regional compendiums and atlases, and the Breeding Bird Surveys and Christmas Bird Counts. A synthesis of the ecology and dynamics of southwestern pine forests (Block and Finch 1997) helps to place information for Grace's Warbler into a larger and historical context. Some gaps are filled by unpublished information, but there is still much to learn about the species, especially those populations breeding south of the U.S. border.
Help author an account about this species from a Neotropical perspective.