New York Status: Special Concern
Federal Status: Not Listed
The cerulean warbler is a small wood warbler of about 4 inches in length, with long pointed wings, a short tail, and long undertail coverts. Males have blue upper parts and white below with black streaking on back and upper tail coverts. Females are bluish-green to olive-green above with white under parts and a white or yellowish eyebrow stripe. Both sexes have 2 white wing bars and white tail spots. Juveniles are similar to female with brownish/gray upper parts, white under parts and a pale crown stripe. The cerulean warbler is often found high in the canopy of mature forests.
The cerulean warbler is an early migrant and arrives on breeding grounds up to 2 weeks before other wood warbler migrants. Males arrive one week before females and pairs form as soon as females arrive. Age of first breeding is one year. Both sexes participate in nest site selection but construction is carried out by the female who may take up to a week to construct the nest.
The nest is a shallow cup consisting of grasses, weeds and mosses, bound on the outside by spider web silk and decorated with white lichens. The nest is usually located in mid-story canopy and is concealed above. Clutch size is 2 to 5 eggs. Incubation is done entirely by the female and lasts 9 to 12 days. Both parents feed the young which fledge after 10 to 12 days. Diet consists primarily of insects gleaned from the upper canopy. Fall migration occurs early and most cerulean warblers return to wintering grounds by August.
Distribution and Habitat
Breeding range extends from the southeastern and south central United States north to southeastern New York and Ontario and west to the Mississippi Valley. It prefers large forest tracts of tall, deciduous, broad-leafed tree species. Territories often occur in the closed canopy of old growth forests near stream bottoms, lakes or rivers. Two principal breeding areas for the cerulean warbler remain in New York: the Finger Lakes highlands and the lowland plain south of Lake Ontario.
The cerulean warbler was designated a species of continental importance for the United States and Canada by the Partners in Flight program. In the late 19th century it was one of the most abundant breeding warblers in the Ohio and Mississippi River valleys. By the mid 1900s, however, it had largely disappeared from most of its former range as a result of habitat loss due to forest fragmentation. In New York it is mostly rare, but locally common in areas where suitable habitat still exists.
Management and Research Needs
The biggest threat to cerulean warbler populations is the fragmentation and loss of mature deciduous forest. Further study is needed to determine the degree of fragmentation tolerated by cerulean populations. Research is also needed to define the minimum forest tract size needed to support breeding populations of cerulean warblers.