Seiurus aurocapilla

Formerly known as Seiurus aurocapillus, but changed for grammatical reasons (AOU 2003).

Large range; still common in many areas, though significant declines have occurred in some regions.

BREEDING: northeastern British Columbia and southern Mackenzie to central Saskatchewan and Newfoundland, south to southern Alberta, western Montana, northern Nebraska, eastern Kansas, northern Alabama, and Carolinas; disjunct population in central Colorado (Van Horn and Donovan 1994, AOU 1998). NON-BREEDING: occasionally in U.S. in southern Texas, Gulf Coast, and North Carolina; most commonly in Mexico, along Pacific coast from Sinaloa south and along Atlantic coast from southern Tamaulipas south; also on Yucatan peninsula; less common throughout Central America, rarely to Colombia and Venezuela; also common in West Indies from central Bahamas to northern Lesser Antilles (fairly common in Puerto Rico and St. John); perhaps annual in Netherlands Antilles (Ridgely and Tudor 1989, Van Horn and Donovan 1994, AOU 1998).

SUMMARY: On the breeding grounds, forest fragmentation has resulted in increased Brown-headed Cowbird (MOLOTHRUS ATER) nest parasitism, increased nest predation by a variety of predators, and reduced pairing and reproductive success. Habitat is also lost or degraded, in the short-term, by clearcutting or other forms of timber harvest that open the canopy.

TIMBER HARVEST: Reduction of the forest canopy is also a threat. Forest thinning associated with recreational cottage construction in Ontario, fuelwood cutting in Massachusetts, and timber harvest in New York reduced habitat suitability (Chadwick et al. 1986, Clark et al. 1983, Webb et al. 1977). In Arkansas, restoration of Red-cockaded Woodpecker (PICOIDES BOREALIS) habitat (midstory hardwood removal followed by burning) eliminated Ovenbirds (Wilson et al. 1995). Habitat changes associated with waste-water irrigation can influence distribution.

This species apparently reaches higher densities than elsewhere in its range within the western boreal forest of Canada, and is threatened there by forest conversion to agriculture along the southern edges of the boreal zone. In Saskatchewan alone, 4368 square kilometers of forest was lost to agriculture in the period 1966-1994, a rate of -0.87%/year (Hobson et al. 2002). Much of the remaining southern boreal forest in western Canada has been leased to forestry companies (Cummings et al. 1994, Stelfox 1995). Deforestation is the primary threat to wintering birds.

NEST PARASITISM: Nests are parasitized by Brown-headed Cowbirds throughout the range (Van Horn and Donovan 1994). Percentage of parasitized nests range from 10% in Quebec (Terrill 1961) to 80% in Wisconsin (Brittingham and Temple 1983). Nest parasitism by Brown-headed Cowbirds decreases with increasing distance from the forest edge. Whereas nest parasitism was 100% within 99 meters of forest edge, it declined to zero 3300 meters from the edge (Brittingham and Temple 1983).

FOREST FRAGMENTATION: Frequency of Brown-headed Cowbird nest parasitism is also influenced by forest fragmentation. Frequency of nest parasitism by Brown-headed Cowbirds was lower in contiguous forested tracts in Missouri (2.5%) and Wisconsin and Minnesota (4%) than in forest fragments in Missouri (66.5%) and Wisconsin and Minnesota (19%; Donovan et al. 1995). In fragmented landscapes, Ovenbirds raise more Brown-headed Cowbirds than in unfragmented landscapes (Porneluzi and Faaborg 1999). Forest fragmentation also decreases male pairing success and nesting success (Burke and Nol 1998, Gibbs and Faaborg 1990, Porneluzi and Faaborg 1999, Porneluzi et al. 1993, Van Horn et al 1995, Villard et al. 1993). Male pairing success varies from zero in small forest fragments within an agricultural landscape to 100% in large tracts (Burke and Nol 1998). However, in managed-forest landscapes, forest fragmentation may not impair male pairing success (Sabine et al. 1996). Forest-dividing roads and powerline corridors can produce edge effects and reduce population density and/or male pairing success (Ortega and Capen 1999, Rich et al. 1994).

PREDATION: The predation rate of 14 nests in oak-hickory forest in Arkansas was 28.6% (Martin 1993). Nest predation may be affected by proximity to forest edge. In a forest fragment within an agricultural landscape, predation of artificial dome nests was significantly greater near the forest edge (<20 meters) than in the forest interior (200 and 400 meters from the edge; Linder and Bollinger 1995). Natural nests in similar forest fragments are also heavily predated (Donovan et al. 1995, Porneluzi et al. 1993). In managed-forest landscapes, however, proximity to edge may or may not influence nest predation. Whereas nesting success was negatively impacted by proximity to edge in a managed-forest landscape in New Hampshire (King et al. 1996), proximity to edge had no influence on nest success in similar habitat in Minnesota (Hanski et al. 1996). Nest predators include various snakes, the Blue Jay (CYANOCITTA CRISTATA), Brown-headed Cowbird, Red Squirrel (TAMIASCIURUS HUDSONICUS), Eastern Gray Squirrel (SCIURUS CAROLINENSIS), Raccoon (PROCYON LOTOR), Striped Skunk (MEPHITIS MEPHITIS), and weasel (MUSTELA sp.). Broad-winged Wawks (BUTEO PLATYPTERUS) prey on young and adults. Suspected predators include the Barred Oowl (STRIX VARIA), American Crow (CORVA BRACHYRHYNCHOS), Common Grackle (QUISCALUS QUISCULA), Deer Mouse (PEROMYSCUS MANICULATUS), Eastern Chipmunk (TAMIAS STRIATUS), Northern Flying Squirrel (GLAUCOMYS VOLANS), Virginia Opossum (DIDELPHIS VIRGINIANA), Red Fox (VULPES VULPES), Domestic Cat (FELIS DOMESTICUS) and Black Bear (URSUS AMERICANUS; Hahn 1937, Reitsma et al. 1990, Van Horn and Donovan 1994).

OTHER: Numerous individuals are killed by striking television towers and other similar tall structures during migration (Taylor and Kershner 1986). In Pennsylvania, less likely to inhabit tracts of forest irrigated with waste-water than non-irrigated forest (Yahner 1995).

WINTERING: On the wintering grounds threatened by deforestation, replacement of diverse native plant communities with agricultural and silvicultural monocultures, and subsistence hunting (Arendt 1992).