CERULEAN WARBLER

Photo Credit: Callie Jo Schweitzer

SCIENTIFIC NAME: Dendroica cerulea (Wilson)

OTHER NAMES: None.

DESCRIPTION: A small (11.5 cm [4.5 in.] long) warbler, with relatively long, pointed wings, and a short tail (Dunn and Garrett 1997). Both sexes have two distinct white wing bars and white tail spots. Adult males cerulean blue above, white below, with a narrow black band across the throat, and streaking on the back and flanks. Adult females blue green above, whitish yellow below, and have a noticeable light buffy or yellowish supercilium. Juveniles similar to adult female in general appearance (Hamel 2000a). Song a fast, three-tiered, accelerating series of buzzy notes, ending with a long, single buzz note, that sounds like zray-zray-zray-zray-ZREEE or zeep-zeep-zeep-zeep-zizizizi-ZEEE (Dunn and Garrett 1997). No subspecies recognized (Hamel 2000a).

DISTRIBUTION: Breeds locally from central Minnesota, central Wisconsin, central Michigan, southeastern Ontario, New York, Connecticut, and Rhode Island south through northern New Jersey, northern Delaware, northeastern Maryland, central Virginia, eastern North Carolina, northern Alabama, east-central Mississippi, southern Arkansas to Missouri, and central and northeastern Iowa (AOU 1998). In Alabama, breeds locally in northern third of state where suitable habitat exists (Imhof 1976). Winters from Columbia and Venezuela south, mostly along the eastern slope of the Andes Mountains, to southern Peru and perhaps northern Bolivia (Dunn and Garrett 1997).

HABITAT: Breeds in large, contiguous tracts of mature deciduous forest with defined layers of sub-canopy trees, shrubs, and herbaceous plants of varying density (Hamel 2000b). Prefers riparian and bottomland forests, and upland, fairly moist, forested slopes with a closed to partially open canopy (Rosenberg et al. 2000). In Alabama, mature bottomland forests along waterways and cove hardwoods preferred (Imhof 1976). Winter habitat includes humid, evergreen, montane forests at elevations ranging from 500 to 1,500 meters (1,640 to 4,920 feet) (Hamel 2000a, b).

LIFE HISTORY AND ECOLOGY: Neotropical migratory birds that arrive on the northern coast of the Gulf of Mexico from late March through early May and proceed north to their breeding grounds (Hamel 2000b). Males typically arrive a week before females to establish territories. Once females arrive, pair bonds formed and nest sites selected (Hamel 2000b). Nests typically placed near the ends of horizontal limbs of deciduous trees in the midstory or overstory canopy. Nest built by female made from bark strips woven together and loosely attached to limb with caterpillar silk or spider webbing; usually decorated with lichens. Clutch size ranges from three to five eggs that are creamy white, or very pale greenish white and blotched with bay, chestnut, or auburn intermingled with spots of drab brown. Incubation solely by female lasts 11 to 12 days. Following hatching, young fed by both parents, whereas brooding done primarily by female. Young fledge after 10 or 11 days. Adults feed fledglings several weeks after young have left nest. Only one brood raised each year (Hamel 2000a, b). Insectivorous, feeding primarily on hymenopterans, lepidopterans, and coleopterans. Foraging takes place high in canopy where insects are gleaned from all portions of leaf structure (Hamel 2000a, b). Following breeding, birds begin moving south in late June, arriving along coasts of Louisiana, Mississippi, and Alabama as early as mid-July (Evans and Fischer 1997, Imhof 1976). Peak fall movement occurs between late July and late August, with most birds having departed by end of September (Hamel 2000b).

BASIS FOR STATUS CLASSIFICATION: Populations have declined significantly nationwide. Breeding Bird Survey (BBS) data since 1966 indicate total population declining 4.2 pecent annually, which is among the highest for all North American breeding birds not currently protected under the Endangered Species Act (Rosenberg et al. 2000). Rapid decline attributed to several factors including the destruction of habitat on breeding and wintering grounds, forest fragmentation, and brood parasitism by brown-headed cowbirds (Hamel 2000a, b; Rosenberg et al. 2000). This prompted Partners In Flight (PIF 2002) to place species on its national Watchlist as an extremely high priority species in need of immediate conservation attention. Little known about current status and distribution in Alabama. Considered a locally common breeder above the Fall Line until the 1970s (Imhof 1976); now known from only a few locations within state. Its drastic decline over the past 40 years is undoubtedly attributed to extensive clear-cutting (Hamel 2000a, b; Rosenberg et al. 2000). For example, areas in west Jefferson, Walker, and northeastern Tuscaloosa Counties that were once primarily forested were later cleared for coal mining operations resulting in the disappearance of the species. Confirmed breeding known from the Sipsey Wilderness Area, Bankhead National Forest, in southern Lawrence County (E. Soehren, pers. observ.) and along Larkin Fork of the Paint Rock River in northwestern Jackson County (A. Lesak, pers. comm.). The assigned priority designation in Alabama is based on its large-scale precipitous decline throughout its distribution, low relative abundance, patchy distribution, dependence on mature, contiguous forests, and continual threats of habitat disturbance and destruction.

Author: Eric C. Soehren