Bird of the Month: Yellow Warbler
By Andy McCormick
PC: Mick Thompson (Yellow Warbler)
Scientific Name: Setophaga petechia
Length 5 in
Wingspan 8 in
Weight 0.33 oz
AOU Band code YEWA
The Yellow Warbler is aptly named for it is the most yellow of all North American wood warblers. The male has a bright, unmarked, yellow face and yellow throat and under parts. It is the only wood warbler with yellow spots in the tail. From below the tail and under tail coverts are entirely yellow. The male has red streaks on its chest, although this feature is quite variable. Its dark black eye is prominent and beady.
The Yellow Warbler is one of a group of warbler species formerly in the genus Dendroica, which now are organized into the genus given the name of Setophaga, the name which has priority for this clade, a group of species with a common ancestor. Setophaga is from the Greek for moth eater, setos, a moth, and phagein, eat. The species name petechia is from petechiae, to refer specifically to small red or purple spots on the skin containing blood. The reference is to the red streaks on the males’ breast (Holloway). Note the yellow tail and undertail coverts.
The habitat of the Yellow Warbler is wet and willowy. It is almost always seen in low brushy areas, although at times it will sit on a higher perch to sing its loud and buoyant Sweet Sweet Sweet Oh-so-Sweet song with an emphatic final Sweet. This warbler is an active forager as it gleans along branches and sometimes sallies out to catch insects on the wing.
In migration Yellow Warblers use all four North American flyways and those that breed farther north migrate very long distances to Central and South America where they winter in brushy habitats, city parks and gardens, and riparian woodlands. They are an early fall migrant leaving the north in July and spend seven months on their wintering grounds.
Yellow Warblers arrive in Washington beginning in mid-April and migration peaks in May. They locate nesting sites in streamside thickets. The open cup nest is built by the female usually within 20 feet of the ground in an upright fork of branches in shrubs and small trees. Four to five greenish-white eggs are deposited and incubated solely by the female for 11-12 days. Young leave the nest in 9-12 days (Kaufman). Yellow Warblers are frequently parasitized by Brown-headed Cowbirds, but they have developed a defensive measure which involves building a new floor on their nest covering the cowbird eggs and then laying new eggs of their own (Lowther, et al).
Although Yellow Warblers are widespread and common in North America, they have had declines in some areas. A subspecies has been extirpated from Texas as a breeder and there have been declines in the Southwest. Brown-headed Cowbirds have been implicated in declines in western states and overgrazing and replanting of riparian habitat have also led to declines. In many parts of the country their preference for second growth areas and woodland edges has helped their population as they move into areas of previous timber harvest.