This colorful warbler has distinct male plumage, but the female black-throated blue warbler is so different that she is often confused as a separate species. Learning more about both genders can help birders better appreciate the beauty of these lovely eastern warblers.
Black-Throated Blue Warbler
- Bill: Small, thin, dark
- Size: 5.25 inches long with 7-7.5-inch wingspan, proportionally large head
- Colors: Black, white, blue, gray, buff, olive-green, brown-gray
- Markings: Males have deep blue-gray upperparts with a contrasting black face, auriculars and throat. Underparts are white with a thick black streak on the flanks. A small white patch may be visible at the edge of the shoulder. The tail is blue-black with white patches, and the wings are black with a broad white patch at the base of the primary feathers. Females show a thin white eyebrow on a gray face with darker auriculars, and a white arc shows below the eye as well. The head and back are brown-gray or olive-green, and a faint blue wash may show on the shoulders and rump. The throat is white and the underparts are buff, but paler on the undertail coverts. The dark wings show a white wing patch, similar to but smaller than the same patch on males. On both genders, the legs and feet are dark. Juveniles look similar to their same gender adult plumages but have less clear markings.
Insects, larvae, fruits, seeds, sap (See: Insectivorous)
Habitat and Migration:
These warblers prefer damp deciduous or mixed coniferous and deciduous woods with a dense understory of shrubs, bushes and thickets, such as shady marshes and bogs. In the summer, their breeding range extends from Newfoundland to southern Ontario, through northern Michigan and along the slopes of the Appalachian Mountains to extreme northern Georgia. In winter, these neotropical migrants retreat to the Caribbean and the western and northern regions of Central America from Nicaragua to Panama. A few black-throated blue warblers will overwinter in southern Florida, and vagrant sightings are occasionally recorded far west of this bird's expected range during migration periods.
The harsh, raspy song of this bird is a slow three syllable tune with a high pitch and loud, drawn out syllables. The final syllable is typically the longest and harshest of the tune, but there is some variation. The call note is a softer, fainter "tip" note.
These warblers are solitary birds or may be found in pairs during the breeding season, and they can seem slow or tame. They hawk insects in flight, returning to the same perch repeatedly to feed. They forage low in the underbrush or as high as midlevel in trees, though rarely at the tops of trees. This can make them harder to see in the shady habitat they prefer, but the male's colorful plumage and white markings can be a bright spot to notice.
These are monogamous warblers. Both the male and female birds work together to build a cup-shaped nest of bark, grass and leaves lined with finer fur, hair and moss. The nest is typically located 1-3 feet above the ground. The 2-5 eggs laid per brood are a pale creamy color lightly flecked with gray-brown specks often concentrated at the larger end of the egg. Only one brood is laid per year.
Black-throated blue warblers will occasionally hybridize with Nashville warblers, which share the same habitat preferences and range.
Attracting Black-Throated Blue Warblers:
These birds, like most warblers, are not particularly common in backyards, but in fall migration or winter they will readily come to feeding areas offering suet or peanut butter. Bird-friendly landscaping that includes shady thickets is especially attractive to these birds, and if pokeberries or similar fruits are planted as a food source, the area can be even more attractive to migrating or overwintering black-throated blue warblers.
Historically, black-throated blue warblers have been vulnerable to habitat loss through deforestation within their range, but in recent decades replanted forests have helped bolster this bird's population without difficulty. They are not considered threatened or endangered, but some nesting success can be limited because they are unwitting brown-headed cowbird hosts. Preserving thick forests can help this warbler continue to thrive.