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Blackburnian Warbler

(Dendroica fusca)
Indianapolis, Indiana

General Information

The Blackburnian Warbler has been rightly called “one of the gems” among the North American warblers. This species, a long distance migrant from southern Central America and South America, also ranges from Columbia and Venezuela to Brazil and the Andes Mountains of Bolivia.

These birds are fairly common, but numbers have been decreasing likely due to habitat loss on the breeding grounds. They breed across Eastern North America from central Saskatchewan to southern Newfoundland, southward through New England and the Great Lakes Region, and along the Appalachian Mountains to North Carolina and Tennessee.

The song, consisting of a series of thin high notes and a higher up-slurred note, is highly pitched and unfortunately for some birders, the highest notes that occur in the middle of the song cannot be heard.

Identification of the first fall female of this species is challenging to say the least. It is very similar to the first fall females of the Cerulean, the Townsend’s, the Bay-breasted and the Blackpoll warbles. Careful inspection can separate these species. See below for some ID tips.
 

First fall females in this species can range from fairly brightly colored to very whitish. This early fall individual shows more color than individuals that would be more whitish later in the fall. The throat and cheek are yellowish to whitish, and lack the burnt orange color of adults (see next image). The grayish auricular patch on the face is lacking in the first fall female Bay-breasted and Blackpoll Warblers, and much paler in the similar Cerulean Warbler.
 

Figure 1- Blackburnian Warbler: First Fall female in basic (winter) plumage

Figure 2- Adult Male Blackburnian Warbler in breeding (alternate) plumage

For comparison, this image of a spring male Blackburnian Warbler shows the spectacular burnt orange color on the throat and face. Compare the white wing patch with the fall wing bars of the female in the preceding and following images.

The throat and supercilium stripe have less yellow than the fall male, and joins the throat patch behind the auricular patch. The supercilium of the female Cerulean Warbler’s does not curve around the rear of the auricular patch to join with the yellow of the neck. The first fall female Townsend’s Warbler has a darker cheek patch outlined with bold yellow.

Figure 3- First fall female Blackburnian Warbler

Figure 4- First fall female Blackburnian Warbler

The throat of the first fall female is washed with white and in some individuals the bird may be even paler.

The pale stripes on the back are diagnostic in the Dendroica Warblers. Note the olive wash especially in the crown and nape.
 

Figure 5- Blackburnian Warbler upper side

Figure 6- Blackburnian Warbler flank

The black streaks on the flank are bold and slightly washed with yellow. Older females show a yellow wash extending to the under tail coverts.

The white tips of the greater and median coverts that produce the white wing bars can be seen in this image. Note the pristine edges of flight feathers at this time of the year.
 

Figure 7- Blackburnian Warbler upper surface of wing

Figure 8- Crown of the female Blackburnian Warbler

The crown may show indistinct black patches and buffy “tramlines.”

The white tips of the greater and median coverts that produce the white wing bars can be seen in this image. Note the pristine edges of flight feathers at this time of the year.
 

Figure 9- Blackburnian Warbler Under tail

Figure 10- Upper tail: Blackburnian Warbler

Feeding habits

The Blackburnian Warbler forages high in the canopy. Many species of insects and other arthropods that infest trees are consumed, including aphids, scale insects, beetles spiders, gnats, ants, termites, mosquitoes, wasps and others. Pokeberries and other fruits are also consumed. Outbreaks of spruce budworms are relished when they occur.

Breeding

Blackburnian Warblers breed in mature coniferous and mixed woodlands. Hemlock, fir and spruce are preferred. The presence of the lichen Usnea seems to be important. The nest is usually built in a conifer even in mixed woodlands. The female builds a cup nest of fine twigs, lichens, mosses, and rootlets lined with hair and fine grasses. Four pale greenish-white eggs with red, brown, and purple spots and streaks incubated by the female hatch in 12 to 13 days. Altricial young are tended by both parents leave the nest in 11 to 12 days. The brood is then split by both parents.

Conservation

Breeding populations of this species are stable and increasing in some areas, and declining in others. Blackburnians are dependent on mature forest. Forest destruction and habitat loss both on the breeding and the wintering grounds have a negative impact on population trends. Parasitism by Cowbirds is uncommon. Their consumption of many insect pests that attack forest vegetation provides a valuable component to the health of forest ecosystems.

Further Reading

Baicich, P. J. and C. J. O. Harrison. 1997. A Guide to the Nests, Eggs, and Nestlings of North American Birds, 2nd Edition. Academic Press, NY. 347 Pp.

Curson, J. D. Quinn and D. Beadle. 1994. Warblers of the Americas. Houghton Mifflin Co., New York. 252 Pp.

Dunn, J. L., K. L. Garrett. 1997. A Field Guide to Warblers of North America. Houghton Mifflin Co., New York. 656 Pp.

Kaufman, K. 1990. A Field Guide to Advanced Birding. Peterson Field Guide series. Houghton Mifflin Co., Boston. 299 Pp.

Pyle, P. 1997. Identification Guide to North American Birds. Part 1. Slate Creek Press, Bolinas, CA. 732 Pp.

Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, D. J. Ziolkowski, Jr., and W. A. Link. 2011. The North American Breeding Bird Survey, Results and Analysis 1966 - 2010. Version 12.07.2011 USGS Patuxent Wildlife Research Center, Laurel, MD

Terres, J. K. 1995. The Audubon Society Encyclopedia of North American Birds. Wings Books, NY. 1,109 Pp.

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