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New Jersey Endangered and Threatened Species Field Guide

Image of An adult Kentucky warbler.Zoom+ An adult Kentucky warbler. © Glen Tepke (

Kentucky warbler

Oporornis formosus

Species Group: Bird

Conservation Status

State: Special Concern (Breeding)



The Kentucky warbler is a small migratory songbird about 5 ½ inches in length. It has an olive-green back, dark cap, and yellow breast. It has broad black “sideburns” which extend downward from the eyes on the head. Both sexes look similar.

This species may be confused with the Canada warbler or the common yellowthroat which are similar in appearance. The Canada warbler has a dark necklace and lacks the dark sideburns whereas the yellowthroat has a black mask rather than sideburns.

The song of the Kentucky warbler also assists with its identification since this species is more often heard than seen. It is a rapid rolling tory-tory-tory-tory or churry-churry-churry-churry, similar to the song of a Carolina wren but lower in pitch.

Image of Range of the Kentucky warbler in New Jersey.Zoom+ Range of the Kentucky warbler in New Jersey.


The breeding range of the Kentucky warbler extends from southern New York in the north to Alabama and northern Florida in the south and as far west as eastern Kansas. It winters in northern South America, Central America, eastern Mexico, and the Caribbean.

Breeding habitat includes wet deciduous forest, dense second growth, and swamps. They prefer forests which have a dense understory. During the winter, they most commonly occupy wet forests.


Kentucky warblers feed on small invertebrates such as insects and spiders. They usually feed on or near the ground, often turning over leaves while searching for prey.


The breeding season for the Kentucky warbler in New Jersey is between early May and mid-August. This species nests on or very near the ground, at the base of a tree or shrub or within a patch of weeds. Nests are built by both sexes and are a loose, bulky cup which may consist of dead leaves, grass, weed stems, bark, and rootlets. Between 3 to 6 eggs are laid in May or June and incubation by the female alone lasts about 12 days. The young are tended to by both parents.


The Kentucky warbler has undergone a decline in population in recent years throughout portions of its range. Such declines are may be due to a number of factors including forest fragmentation, brood parasitism by cowbirds, loss of understory due to overgrazing by deer, and predation of nests. It is listed as a Species of Special Concern in New Jersey (not yet endangered or threatened but possibly on its way).

Preservation of large intact forest with dense understory benefits this species. Conservation of New Jersey’s warbler species requires long-term monitoring and research, habitat preservation and restoration, 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: Oporornis
                   Species: O. formosus

Find Related Info: Special concern, Migratory songbirds

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