Dendroica fusca
Blackburnian warbler

Blackburnian warblers are commonly found throughout southeast Canada, from Alberta into the Great Lake areas to Newfoundland and into the Appalachians as far south as Georgia during the summer season. However, during migration, this species is seen throughout the eastern coast of North America and as far west as Oklahoma. For the most part, they migrate over the Gulf of Mexico; however, some fly over the eastern coast of Texas. During the winter they can be found in Costa Rica, Panama, and into Peru. (Morse, 1994; Rappole, 1995)

Blackburnian warblers inhabit deciduous and coniferous forests during the summer. They prefer coniferous forests, but will be found in spruce trees or hemlock in deciduous forests. In any forest type in their summer range, blackburnian warblers are most active foraging and vocalizing in conifers. Tree species preferred by blackburnian warblers are pines Pinus, spruces Picea, and hemlocks Tsuga. They prefer the upper third of tree canopies in dense, mature forests. During the winter they are found in wet forests from Panama into South America. (Greenberg, 1979; Lawrence, 1953; Morse, 1994; Young, et al., 2005; Zerda Lerner and Stauffer, 1998)

Male blackburnian warblers are easily identified by their orange throat, breast and forehead. They have a black crown and cheeks and are noted for their wing bars and tail spots. Blackburnian warblers have white bars on a black back, wings, and tail. There are black streaks on a white background on the sides and flanks. The lower breast and stomach is slightly orange, fading to white towards the tail.

Females have a pale orange to yellow faces and breasts, with brownish crowns, cheeks, and wings. There are two bars of white on the wings. Females also have white bellies and undertail coverts with grayish streaks on her sides and flanks.

Blackburnian warblers are, on average, 13 cm in length with a wingspan of 21 cm. Like most warblers, they have small, flattened, and short bills, and have thin, black legs with 3 toes in front and one in back (Sibley, 2001). (Morse, 1994; Sibley, et al., 2001)

Male blackburnian warblers attract their mates by singing in tree tops. When a potential mate comes close, males flick their tail and peck at the branch. Males defend their mate from other males by flicking their tail, pecking at branches, and occasionally fighting. Blackburnian warblers, like other songbirds, are socially monogamous. Males typically help raise and feed the young. In some cases they have been absent, likely due to occasional extra-pair copulations. (Lawrence, 1953; Nice, 1926)

Blackburnian warblers typically nest in the higher canopy of the tallest trees. Their nest usually consists of twigs attached by spider silk, dry spruce twigs and bark, the inside consists of dead pine needles and grasses in the shape of a fine cup positioned away from the trunk and hidden in the foliage on the horizontal branches. Females are the primary builders and will take 3 to 6 days to build nests. They start building nests close to the time they lay eggs. They typically breed between May and July, with 1 brood per year of 4 to 5 eggs. The eggs hatch in about 2 weeks and the young fledge between 2 and 4 weeks. Females are usually in their second year of life before breeding. Males have been known to breed while they are still subadults (less than 1 year old), but are more successful and more likely to breed in their second year of life. Males help feed females while incubating eggs. However, she will spend some time off of the nest. (Lawrence, 1953; Nice, 1926)

Blackburnian warblers spend, on average, 22 minutes on the nest and 5 minutes off the nest after the eggs hatch. Both males and females feed the young, females more so than males. Males feed more than one hatchling at a time and females typically only feed one young at a time. They feed the young every 10 to 20 minutes. They take 2 to 4 weeks until the young fledge, both parents care for the young during that time. It takes several months before the young are independent of the parents. (Lawrence, 1953; Morse, 1994; Nice, 1926)

Blackburnian warblers live in the wild for a average of 3 to 6 years. The primary cause of death is not surviving through migration. Because of poor weather or insufficient energy stores, death is more common during spring migration, especially when flying over the Gulf of Mexico. Blackburnian warblers are not kept in captivity. (Dunn and Garrett, 1997; Elphick, et al., 2001; Morse, 1994; "Reference Atlas to the Birds of North America", 2003)

Blackburnian warblers usually fly in mixed-species flocks. Typically there are 1 to 2 blackburnian warblers per flock, but there can be as many as 7. They are not very social with each other or other species other than foraging near each other. They have learned to co-exist with other species and avoid direct competition by staying in the upper third of the tree canopy and foraging and nesting on the outside of the branches, a form of niche partitioning. Even in the same habitats and with similar food sources, different species of the Dendroica are able to survive in separate niches. (Lawrence, 1953; MacArthur, 1958; Morse, 1994)

Blackburnian warblers typically live in a 0.4 to 1.1 hectare area. However, they live on small islands if there are tall, mature trees and suitable food sources. (Morse, 1967; Morse, 1994)

Blackburnian warblers sing at dusk and dawn in the frequency range of 4 to 12 KHz. They typically sing the same song at both times. Males duet during these times and sing at each other after hostile encounters with other males. Males are usually stationary, perched higher in tree than females when singing. Singing is used to advertise for breeding and to advertise territories. They have two distinct song types, occasionally alternating them during breeding season. They flick their tail and peck at branches while singing during breeding season. Blackburnian warblers sing one song while stationary at the top of the tree and during encounters with other males. They chirp twice frequently throughout aggressive encounters with other males. The other song is primarily used while foraging and while in the presence of a female. Blackburnian warblers who do not find mates sing the second song type for long periods of time. (Morse, 1967; Morse, 1989)

Blackburnian warblers are insectivorous, diurnal foragers, usually gleaning insects from leaves. They also hover to capture insects from the bottom of leaves. They feed on caterpillars, mayflies, mosquitos, gnats, spiders, and other small invertebrates. (Crawford and Jennings, 1989; Lawrence, 1953; Morse, 1994)

Blackburnian warblers are typically preyed on by larger birds of prey and some mammals. Most predation is on eggs, hatchlings, and fledglings, or on adults as they watch and defend nests. Hawks are the most common predators. (Lawrence, 1953; Morse, 1994)

Blackburnian warblers are known for their increased presence during spruce budworm (Choristoneura species) breakouts, in which their survival and reproduction are greater because of the abundance of prey. These warblers are also well-known for interspecific niche partitioning. Which is how they avoid direct competition with species of the same genus; they coexist by using different parts of the same tree for nesting and foraging.

Blackburnian warblers are used as hosts by mites and lice. (Betts, et al., 2006; Betts, et al., 2007; Crawford and Jennings, 1989; Morse, 1994; Peters, 1936; Schulte, et al., 2005; Zerda Lerner and Stauffer, 1998)

Blackburnian warblers are strong indicators of mixed deciduous-coniferous forests and undisturbed, mature coniferous forests. Surveyors use this species to study the ecology and effect of forest fragmentation by timber harvesting. They are also important for controlling spruce budworm (Choristoneura species) outbreaks. (Betts, et al., 2006; Betts, et al., 2007; Crawford and Jennings, 1989; Schulte, et al., 2005; Zerda Lerner and Stauffer, 1998)

There is no known negative impact of blackburnian warblers on humans.

Currently, blackburnian warbler populations are not considered threatened. However, wintering habitats are rapidly declining and they are sensitive to forest fragmentation. (Morse, 1994)