The Black-throated Blue Warbler is a small songbird that is found in the eastern parts of North America. Here are some interesting facts about this warbler species:
Identification
The Black-throated Blue Warbler gets its name from the black throat and blue-gray feathers on the back of the adult males. The females and immatures are duller in color with a gray head and back and a white throat and belly. These warblers have a distinct white wing bar and white spots on the outer tail feathers which helps identify them.
Size and Weight
The Black-throated Blue Warbler is a small bird, measuring 4.7-5.1 inches in length and weighing 0.3-0.4 ounces on average. This makes them one of the smallest warbler species found in North America.
Habitat
This warbler nests in mature deciduous and mixed forests in the eastern US and Canada. They prefer large tracts of unfragmented forest with a dense understory. During migration, they can be found in a wider variety of woodlands, forests, and shrublands.
Breeding
Black-throated Blue Warblers breed in the northern parts of their range from May to July. The female builds an open cup nest out of bark strips, grasses, pine needles, and spider webs usually low in a shrub or sapling. She lays 3-5 eggs which she incubates for 11-12 days. The chicks fledge from the nest in 9-12 days.
Diet
This warbler is primarily insectivorous, feeding on insects and spiders that it gleans from foliage and branches. Caterpillars make up a large part of its diet during the breeding season. They also eat beetles, moths, flies, leafhoppers, spiders, and other small arthropods.
Migration
The Black-throated Blue Warbler migrates long distances between its breeding and wintering grounds. They breed primarily in the northeastern US and southeastern Canada and migrate through the eastern states in April and May to their wintering grounds in the Caribbean. In August through October, they migrate back through the eastern US to return south again.
Conservation Status
According to the IUCN Red List, the Black-throated Blue Warbler has a conservation status of Least Concern. The global population is estimated at 3.5 million individuals and is generally stable, though some local declines have occurred. Loss of wintering habitat in the Caribbean is a potential threat.
Interesting Facts
- Male Black-throated Blue Warblers perform a zigzagging flight display during courtship to attract females.
- Their song is a buzzy “zee zee zee zo zee” which carries far through the forest.
- They sometimes hybridize with other closely related warbler species where their breeding ranges overlap.
- The oldest known wild Black-throated Blue Warbler was over 7 years old when it was recaptured and rereleased during banding studies.
- John James Audubon painted this species in 1812 based on a specimen collected in Kentucky.
Population Trends
According to data from the North American Breeding Bird Survey, Black-throated Blue Warbler populations declined by about 1.3% per year between 1966 and 2015. However, more recent analysis of data from migration monitoring stations suggests the population has been stable in the short-term since 2005.
Year | Estimated Population |
---|---|
1966 | 3.6 million |
2015 | 3.4 million |
So while there may have been a slight long-term decline, Black-throated Blue Warbler numbers seem to have leveled off more recently. Continued monitoring is needed to ensure populations remain stable.
Range and Distribution
The Black-throated Blue Warbler breeds in two separate areas of eastern North America:
- The northern part of their range extends across northern Minnesota, Wisconsin, Michigan, southern Ontario, upstate New York, Vermont, New Hampshire, Maine and the southern Maritime provinces of Canada.
- There is also a disjunct southern breeding population in the higher elevations of the Appalachian Mountains from Georgia to Pennsylvania.
In the winter, the entire population migrates to the Greater Antilles in the Caribbean including Cuba, Jamaica, Hispaniola, and Puerto Rico. See the range map below:
The species occupies a relatively small global range of less than 500,000 square kilometers. However, habitat across most of its range remains intact which contributes to its current population stability.
Taxonomy
The Black-throated Blue Warbler was one of the many bird species originally described by Linnaeus in the 18th century. Its scientific name is:
- Kingdom: Animalia
- Phylum: Chordata
- Class: Aves
- Order: Passeriformes
- Family: Parulidae
- Genus: Setophaga
- Species: caerulescens
This places the Black-throated Blue Warbler in the diverse order Passeriformes which contains more than half of all bird species. They belong to the New World warbler family Parulidae.
Similar Species
The Black-throated Green Warbler and Blackburnian Warbler have similar names and overlapping ranges with the Black-throated Blue, but can be distinguished by differences in color patterns. The Black-throated Green has green back feathers while the Blackburnian has an orange throat patch.
Behavior and Ecology
Foraging
The Black-throated Blue Warbler forages by gleaning insects from leaves and branches in the lower to mid-levels of forest trees and shrubs. They are very active foragers, able to hover and hang upside-down as they pick insects from foliage. Caterpillars are a preferred food source.
Social Behavior
These warblers are territorial during the breeding season, with the male defending a territory from other males. They are otherwise solitary nesters, coming together only for courtship and mating. Outside of the breeding season, they may form loose flocks with other warbler species while migrating.
Vocalizations
As mentioned above, the male’s song is a buzzy “zee zee zee zo zee.” Both sexes also use call notes like chips and seets to communicate. The call notes are often the best way to detect these birds as they can be hard to see among the foliage.
Predators and Threats
Nest predators like squirrels, snakes, and birds will take eggs and nestlings. Hawks, owls, and other birds prey on the adults. Collisions with buildings, vehicles, and towers during migration also kill many individuals each year. Habitat loss on the wintering grounds is another concern for the species’ long-term outlook.
Conclusion
In summary, the Black-throated Blue Warbler is an energetic and strikingly colored songbird species. Their long-distance migration, habitat preferences, interesting courtship displays, and diverse vocalizations make them a fascinating focus of research and observation for bird enthusiasts. Maintaining adequate breeding habitat as well as conserved wintering grounds will be important for the continued success of these warblers.