PIF Priority Bird for Southern Blue Ridge,
The Blackburnian Warbler is a striking neotropical migratory bird. The bright orange, black and white colors of the adult male are very distinctive. It is a breeder in coniferous forests of the northeastern United States, parts of Canada and the Appalachians. The Genus name Dendroica basically translates to ‘tree-dwelling. Some wood warblers in the Genus Dendroica coexist during the breeding season, particularly in coniferous northeastern habitats, by foraging in different niches of the same forests. This is a very insectivorous warbler, especially during the breeding season. It seems to eat a lot of lepidopteran larvae, which it gleans from foliage high in the canopy. This species seems to be holding its own, at least for now, despite losing wintering and breeding habitat in some parts of its range. Many of these birds winter in South America and face perilous migration journeys back and forth each year. It is a conspicuous springtime singer from high, exposed perches.
History and Status
On the breeding grounds this bird nests in coniferous forests, though it sometimes inhabits deciduous or deciduous-coniferous forests as well in the southern parts of its range. It is a neotropical migrant that winters in lower Central America and northern South America. Neotropical (New World) migratory birds breed during summer in temperate North America, migrating north each spring from wintering areas, then fly back south to spend the bulk of the year in Mexico, Central or South America, or the Caribbean.
In some parts of the northeast, there are some minor range expansions and populations are likely increasing as areas reforest and age. The Breeding Bird Survey (BBS) shows little overall change in population numbers from 1966 to 1990. Care should be taken in interpreting data from a roadside survey such as BBS for forest-interior species. Increases occurred in some areas and decreases in others over the last 30 years.
Description
This is a rather small warbler. Most adults, and all males, are unique with an orange throats and breast coloration. Females during the breeding season are somewhat duller than males. On the breeding grounds, this species is readily identified by sight. Perhaps the adult female could be confused with the Yellow-throated Warbler, but it usually has a small yellow crown patch and a much smaller bill.
Habitat and Habits
Exploiting a treetop niche, the Blackburnian Warbler breeds in coniferous forests, and in the south also utilizes deciduous and deciduous-coniferous forests. During migration this species regularly uses all woody habitats, including maritime scrub with dense bayberry thickets. On the wintering grounds it is most often found in highland or montane forests of South America. It has also been documented wintering on coffee plantations in Venezuela and Columbia.
Males sing during the breeding season frequently at dawn and dusk when it is too dark to forage. Singing predominates in the morning hours, with bouts of foraging becoming more common later in the day. Blackburnian Warblers have a confusing variety of song types that they use, and can be confused with singing American Redstarts. One common primary song has a very high pitched ending that seems to go off our hearing scale at the end.
As with many wood warblers, the females lag behind adult males by several days during migration. Nests are almost always placed in conifers, with hemlocks a common choice if it is present. Most nests are placed well up in the tree canopy, and are placed on limbs well out from the trunk. Females are thought to build the nest and perform incubation chores. The cup-like nest is usually well hidden. It is typically constructed from twigs, bark, plant parts and rootlets, and lined with lichens, mosses, fine grasses, animal hair and even exotic substances like string. Evidently birds often travel considerable distances to secure nest material.
This bird eats mainly insects and other small invertebrates during the breeding season. It typically feeds by gleaning tips of small branches and twigs, usually high in the tree. Some birds also feed on the underside of vegetation by hovering and also hawk flying insects. In some parts of its breeding range, males forage much higher than females. Breeding birds in coniferous forests often concentrate on lepidopteran larvae. Other common foods include mayflies, flies, beetles, true bugs and spiders.
Range and Distribution
The Blackburnian Warbler breeds in the northeastern United States, parts of eastern Canada and throughout the Appalachian Mountains. They winter mainly in northern South America and south in the Andes to Peru, but also in southern Central America. Generally it is thought to migrate mostly at night, with most birds crossing the Gulf of Mexico in springtime. It may progress rather slowly northward in spring, often moving only around a dozen miles per day.
People Interactions
Some birds likely collide with man-made structures like TV towers and buildings during migration. The heavy use of pesticides has been documented to cause mortality, especially events related to spruce budworm control in the northeast. Removal of large conifers can decrease populations of this species on the breeding grounds, and deforestation on the wintering grounds will likely become a serious problem in the near future. In the mountains of North Carolina, high elevation populations have certainly been affected by the loss of most of the mature fraser’s fir due to mortality accelerated by an exotic insect pest, the balsam woolly adelgid, during the later part of the 20th century. Birds are now frequently found between 3,000 and 4,500 feet in out mountains, often keying on large conifers like spruce, white pine and eastern hemlock. A future threat exists from another exotic adelgid species that attacks hemlocks.
American Warblers, by Morse, 1989, Harvard University Press
Peterson Field Guides: Warblers, by Dunn and Garrett, 1997, Houghton Mifflin Co.