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New Jersey Endangered and Threatened Species Field Guide


Image of An adult male black-throated blue warbler.Zoom+ An adult male black-throated blue warbler. © Blaine Rothauser

Black-throated blue warbler

Dendroica caerulescens

Species Group: Bird

Conservation Status

State: Special Concern (Breeding)

 


IDENTIFICATION

The black-throated blue warbler is a small migratory songbird about 5-5 ½ inches in length. The male is blue-gray above with a black throat, black sides, white belly, and a small white patch on the wing. The female is brown-backed with a buff belly, a light line over the eye, and a small white patch on the wing.

Image of Range of the black-throated blue warbler in New Jersey.Zoom+ Range of the black-throated blue warbler in New Jersey.

DISTRIBUTION AND HABITAT

The breeding range of the black-throated blue warbler extends from southern Ontario in the northwest, throughout southeastern Canada to Nova Scotia in the northeast and extends southward along the Appalachian Mountains as far south as northern Georgia. It winters primarily in the West Indies and may also winter in Central America.

Breeding habitat includes understory of deciduous and mixed woodland, second growth, and partially cleared forest. They require forested habitats with a dense, well-developed shrub layer, both for nesting and foraging. During the winter, their habitat consists of dense forests within mountainous interiors of large islands or in rich lowland forest.

DIET

Black-throated blue warblers feed on insects, as well as seeds and fruits. They forage among understory shrubs, ferns, and in forest mid-story.

LIFE CYCLE

The breeding season for the black-throated blue warbler in New Jersey is between mid-April and early to mid-August. They nest in small trees, saplings, or shrubs in dense undergrowth within approximately a meter of the ground. The nest is constructed primarily by the female. Between 3 to 5 eggs are laid in May or June and the female incubates them by herself for about 12 days. The young are tended to by both parents and leave the nest at ten days old. They may have up to three broods within a nesting season.

CURRENT STATUS, THREATS, AND CONSERVATION

The black-throated blue warbler is listed in New Jersey as a Species of Special Concern (not yet endangered or threatened but possibly on its way). They are at risk due to their need for large, intact forest habitat both during the breeding and non-breeding seasons. Forest fragmentation within their breeding range eliminates suitable habitat and increases the threat of nest parasitism by brown-headed cowbirds (Molothrus ater). Tropical deforestation within their winter range is a threat as well especially because of the relatively small winter range of the species.

Preservation of large areas of habitat with some site disturbance which promotes the development of a dense shrub layer benefits this species. Conservation of New Jersey’s warbler species requires long-term monitoring and research, habitat preservation and restoration, reduction in mortality caused by humans, cowbird control, and incentives to promote habitat preservation within their wintering areas.


Text written by Michael J. Davenport in 2011.


Scientific Classification

Kingdom: Animalia
    Phylum: Chordata
       Class: Aves
          Order: Passeriformes
             Family: Parulidae
                Genus: Dendroica
                   Species: D. caerulescens

Find Related Info: Migratory songbirds, Special concern

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