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black-throated blue warbler

Dendroica caerulescens

What do they look like?

Black-throated blue warblers are about 13 cm long and from 9 to 10 g. Males and females have different color patterns. Males have dark blue backs and black faces, throats, and sides. Their bellies and breasts are white. Females are olive green with buffy yellow throat, breast, and bellies. Females have a buffy eye stripe, a white semicircle below the eye, and a small white wing spot. Immature males have a greenish tinge to the feathers on their back. They have black legs, feet, and bills.

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range mass
    9 to 10 g
    0.32 to 0.35 oz
  • Average length
    13 cm
    5.12 in

Where do they live?

Black-throated blue warblers are found in northeastern North America in the summer, breeding season. They are found from the northern Great Lakes region east to the Canadian maritime provinces, throughout New England, and south through the Appalachian mountains. In winter they are found in southernmost Florida, the Antilles south to Trinidad, and the coastal Yucatan peninsula, from Mexico and Belize to Honduras. (Holmes, et al., 2005)

What kind of habitat do they need?

Black-throated blue warblers are found mainly in areas of undisturbed deciduous and mixed-deciduous forests in their breeding range. They prefer forests with a dense, shrubby understory. In winter they are found in tropical forests, including secondary forest, plantations, and disturbed forest fragments.

How do they reproduce?

Black-throated blue warblers form bonds between males and females each breeding season. Sometimes males try to have two female mates. Pairs are formed very soon after arriving at the breeding site. Males guard their mates closely.

Black-throated blue warblers start breeding in late May and can breed into August. Females find nest sites and build nests out of strips of bark, cobwebs, and saliva. They line them with softer materials, like moss, hair, pine needles, or shredded bark. Females usually lay 4 white, speckled eggs in a clutch. Most females lay 2 clutches a year, either after losing a clutch to predators or after having successfully raised a brood. Incubation takes 12 to 13 days and young begin to fly between 8 and 10 days after hatching. They leave the nest at that point, but remain nearby and are fed and protected by their parents for another 2 to 3 weeks after they have begun flying. Black-throated blue warblers can breed in their first year after hatching.

  • How often does reproduction occur?
    Black-throated blue warblers breed seasonally and may attempt several clutches in a season, usually 2.
  • Breeding season
    Black-throated blue warblers breed from late May through July or August.
  • Range eggs per season
    2 to 5
  • Average eggs per season
  • Range time to hatching
    12 to 13 days
  • Range fledging age
    8 to 10 days
  • Range time to independence
    22 to 31 days
  • Range age at sexual or reproductive maturity (female)
    1 (low) years
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Range age at sexual or reproductive maturity (male)
    1 to 2 years

Females incubate the eggs and brood hatchlings. Males will feed females while they are on the nest. Young hatch with their eyes closed and naked. Their eyes open at about 4 days old and they leave the nest at 8 to 10 days old, when they are just beginning to learn to fly. Males and females both feed nestlings and fledglings for up to 3 weeks after they leave the nest. Both parents protect their young from predators with alarm calls and by trying to distract predators by pretending to have a broken wing.

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

How long do they live?

The oldest recorded black-throated blue warbler was at least 10 years old.

  • Range lifespan
    Status: wild
    10 (high) years

How do they behave?

Black-throated blue warblers flit among vegetation and can hop on the ground. They are migratory and active during the day. They spend much of their time foraging, except when females are incubating eggs or brooding young, when they spend 75% of their time incubating or brooding. They are solitary throughout the year, except for mated pairs during breeding season. Males defend territories for feeding and nesting.

Home Range

Foraging and nesting territories are from 1 to 4 hectares in size during the breeding season. In winter, foraging territories are from 0.2 to 0.3 hectares for males and slightly smaller for females.

How do they communicate with each other?

Black-throated blue warblers use a series of calls and songs to communicate. Males do most of the singing. The two most common songs are: 1) a song of 3 to 7 buzzing notes that trills upward at the end, sounding like "zee-zee-zee-zreeee," and 2) a song of 2 to 5 notes that descends at the end, sounding like "zee-zee-zhurrr." Most songs are used during the breeding season, but there is some singing during migration and in winter. Males sing from perches in their home range.

What do they eat?

Black-throated blue warblers eat mainly insects, but they will eat some fruits during the winter. They eat mainly beetles, caterpillars, butterflies and moths, flies, bugs, and spiders. Black-throated blue warblers forage by themselves among leaves and on branches. They take most of their prey from leaves and bark.

  • Animal Foods
  • body fluids
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • fruit
  • nectar

What eats them and how do they avoid being eaten?

Black-throated blue warbler adults are preyed on by birds of prey, such as Cooper's hawks. Eggs and nestlings are taken by a wide variety of nest predators, including sharp-shinned hawks, blue jays, red squirrels, eastern chipmunks, martens, fishers, flying squirrels, raccoons, black bears, and garter snakes. Black-throated blue warblers will mob predators and perform broken-wing displays to distract them.

What roles do they have in the ecosystem?

Black-throated blue warblers are important predators of insects in their forest habitats. They may also help to disperse seeds of the fruits they eat. There are few reported parasites in black-throated blue warblers. Brown-headed cowbirds will lay their eggs in the nests of black-throated blue warblers, especially in areas of disturbed forest.

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

There are no known adverse effects of black-throated blue warblers on humans. However, along with many other bird species, they carry West Nile virus. (Holmes, et al., 2005)

  • Ways that these animals might be a problem for humans
  • injures humans
    • carries human disease

How do they interact with us?

There is no direct positive impact of black-throated blue warblers on humans. However, they are lovely and interesting members of native faunas and may attract bird watching interest. (Holmes, et al., 2005)

Are they endangered?

Black-throated blue warblers are not considered threatened currently. Although they may be sensitive to forest destruction and prefer large, undisturbed areas of forest, they seem to tolerate disturbed forests in their breeding and winter ranges.


Tanya Dewey (author), Animal Diversity Web.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


living in landscapes dominated by human agriculture.


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.


an animal that mainly eats meat


uses smells or other chemicals to communicate

  1. active during the day, 2. lasting for one day.

animals that generate their own body heat through metabolic processes.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


makes seasonal movements between breeding and wintering grounds


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


having more than one female as a mate at one time


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Climbing plants are also abundant. There is plenty of moisture and rain, but may be somewhat seasonal.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


Holmes, R., N. Rodenhouse, T. Sillett. 2005. Black-throated Blue Warbler (Dendroica caerulescens). The Birds of North America Online, 87: 1-20. Accessed April 18, 2009 at

University of Michigan Museum of ZoologyNational Science Foundation

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Dewey, T. 2009. "Dendroica caerulescens" (On-line), Animal Diversity Web. Accessed April 16, 2014 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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