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Blackburnian Warbler
Setophaga fusca
NatureServe conservation status
Global (G-rank): G5
State (S-rank): SNA
External links
Species range
BREEDING: central Saskatchewan and central Alberta east to Nova Scotia and southwestern Newfoundland, south to southern Manitoba, Great Lakes region, southern Appalachians (to Georgia), and southern New England (Morse 1994, AOU 1998). NON-BREEDING: mid-elevations from Costa Rica and Panama (rarely) south to Colombia and Venezuela and along slopes of Andes of Ecuador, Peru, and northwestern Bolivia (Morse 1994, AOU 1998). In South America, most common in Colombian Andes (Ridgely and Tudor 1989). Transient in eastern Mexico and northern Central America; accidental in Caribbean during migration.
Migration
Migrates through Costa Rica late August-late October and in April (Stiles and Skutch 1989). Present in South America mostly September-April, sometimes May (Ridgely and Tudor 1989).
Habitat
BREEDING: Coniferous (primarily balsam fir or hemlock) and mixed forest, open woodland, second growth. In Upper Michigan, breeds in natural, older age (60-167 years old), pole, and sawlog size-class stands on mesic upland sites, with canopy closure averaging 80 percent and basal area of conifer trees about three times greater than that of hardwoods (Doepker et al. 1992). There may be some preference for red spruce over white spruce (Morse 1976). Tall trees are important; birds seldom nest in forests without substantial vegetation over 18 meters (Morse 1971, 1976). Loss of forest canopy in the black spruce-Fraser fir forest on Mount Mitchell, North Carolina, from 1959 to 1985 correlated with warbler disappearance (Adams and Hammond 1991). Nests on horizontal branch of conifer, well out from trunk, in site well concealed by foliage or lichen, 2-24 meters above ground. NON-BREEDING: In migration in various forest, woodland, scrub, and thicket habitats (AOU 1983). In winter, forests and woodlands of mountain slopes; forest canopy and edge, semi-open areas, tall second growth (Stiles and Skutch 1989). De La Zerda Lerner and Stauffer (1998) report a preference for dense trees, shrubs, and snags, with use of both large forest fragments and small or linear patches, but not solitary trees in pastures or non-native pine plantations. Birds were observed most commonly in the upper third of tree canopies.
Food habits
Eats insects, also berries; forages among leaves and twigs high in upper branches or in outer foliage, also flycatches. In breeding areas, forages generally above 10.6 - 12.1 meters; in a wintering area in Colombia, foraged commonly at lower levels as well (Chipley 1980).
Ecology
In a study in Maine, appeared to depress numbers of black-throated green warblers (DENDROICA VIRENS) where they coexisted (Morse 1976). Usually solitary in winter but may join mixed flocks (Stiles and Skutch 1989, Ridgely and Tudor 1989).
Reproductive characteristics
Eggs laid mostly late May to June. Clutch size four to five (usually four). Incubation about 11-12 days, by female. Young tended by both parents.
Threats or limiting factors
HABITAT: Loss of tropical broad-leaved forests in the wintering areas in South America poses a significant threat. Diamond (1991) predicted (based on projections of the Food and Agricultural Organization of the United Nations) that habitat area in 2000 would be only 66 percent of that available in 1985 due to logging and the conversion of forests to agriculture. Considered "highly vulnerable" to alterations of its winter habitat; included on a list of 45 long-distance migratory land birds most likely to suffer from such alterations (Petit et al. 1993, 1995). Reforestation of cleared areas with non-native tree species which are avoided by wintering birds is a special concern (De La Zerda Lerner and Stauffer 1998). PREDATION: Nest predators include red squirrels (TAMIASCIURUS HUDSONICUS) and blue jays (CYANOCITTA CRISTATA), but these do not seem to control populations (Stewart and Aldrich 1952). PARASITISM: Brown-headed cowbird (MOLOTHRUS ATER) parasitism not likely a significant limiting factor (Morse 1994).
