Black-throated Blue Warbler
Dendroica caerulescens
Description
The plumage
of the Black-throated Blue Warbler differs more dramatically between males
and females than any other wood-warbler species. The male has a black
face, throat and flanks, dark blue upperparts, whitish underparts and
a large white wing patch. The female is greenish grey with a distinct
white wing patch and a whitish cream-coloured stripe over the eye. Similarly,
first year males have greenish dorsal tract feathers.
Habitat
The Black-throated
Blue Warbler typically nests in undisturbed deciduous and/or mixed woods
with a thick understorey.
Song
It is almost exclusively the male that does all of the singing and consists of a series of 3 to 5 buzzy "zwee" notes as represented by "zwee zwee zwee zweee" or "zee-zee-zee-zeeeeee".
Similar Species
The male is completely unmistakable but the female may be confused with other drab olive warblers. Key features to note are the dark face mask and the white patch on the wing.
Comments
This species
spends much of its time foraging for insects low in the brush and foliage
of their habitat, with the male expanding its foraging range somewhat
higher than that of the female.
Due to the high degree of sexual dimorphism in plumage colouration, early naturalists such as Wilson (1810) and Audubon (1841) originally considered the male and female Black-throated Blue Warbler to be separate species.
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