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Dendroica nigrescensblack-throated grey warbler

By Ginger Frogel

Geographic Range

The range of Dendroica nigrescens, the black-throated gray warbler, extends westward from the Rocky Mountains to the western coast of the United States. It extends northward to southwestern Canada and southward into Central America. During the colder months, typically September, the black-throated gray warbler migrates southward through California.

By October, their nonbreeding season, they can be found in Brazil and Mexico. During the breeding season, they migrate northward to North America where they are found nesting in Arizona and California. There are rare documentations of vagrant isolated birds being found as far as the Atlantic coast in Virginia and Georgia in the fall season. (Bent, 1963; Dunn and Garret, 1963; Goodbred and Holmes, 1996; Martin, 1980; Morse, 1989; Stokes and Stokes, 2004; Thorton, 1999)

Habitat

Mostly known for its short migratory behavior, the black-throated gray warbler is commonly found in the temperate and tropical regions of North and Central America. The black-throated gray warbler lives in short shrubbery provided by dry climates where the humidity does not usually reach above 44%. It can be found in grassy scrub forests and chaparral along the western coast of Mexico and predominately, California, Arizona, and New Mexico. Occasionally, they are found in riparian zones, and mangroves with scrubby habitat.

During migration, the black-throated gray warbler is found in Central America. Before breeding season they migrate through the western region of North America. This warbler rests in juniper trees (Juniperus osteosperma) and pinyon pines (Pinus cembroides) until it reaches the tropical chaparrals in Mexico and Central America for the non-breeding season.

There have been cases of vagrants reaching the Atlantic coast of North America. Here, these vagrants also reside in chaparrals and shrubby habitats.

Reported elevations range from 137.2 to 1219.2 m. (Barlow, 1899; Bent, 1963; Curson and Quinn, 1994; Goodbred and Holmes, 1996; Guzy and Lowther, 2012; Harrison, 1984; Martin, 1980; Morse, 1989; Scott, et al., 2000; Stephenson and Whittle, 2013; Stokes and Stokes, 2004; Thorton, 1999)

  • Range elevation
    137.2 to 1219.2 m
    450.13 to 4000.00 ft

Physical Description

The black-throated gray warbler is a small song bird ranging from 11-13 cm in length and 7-10g in weight. The male and female are relatively the same size, both with wingspans of 7.5-8.0 cm.

The black-throated gray warbler can be identified by its multi-colored plumage. Both males and females have black crowns, small yellow spots above or below the eye, a gray back, and white wing-bars. The notable difference between the male and female black-throated gray warbler is the difference in chest color. The female has a white chest while the male has a black chest, and both contain vertical black and white striping on their chests and white spots on their tails.

The immature male black-throated gray warbler shows physical characteristics close to that of the adult female. The immature male has a white or gray chest that does not darken in color until full maturation. During spring and summer, the black-throated gray warbler plumage is notably lighter in both sexes. (Barlow, 1899; Bent, 1963; Curson and Quinn, 1994; Dunn and Garret, 1963; Gilfillan, 2010; Harrison, 1984; Martin, 1980; Morse, 1989; Stephenson and Whittle, 2013; Stokes and Stokes, 2004; Thorton, 1999)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range mass
    7 to 10 g
    0.25 to 0.35 oz
  • Range length
    11 to 13 cm
    4.33 to 5.12 in
  • Range wingspan
    7.5 to 8 cm
    2.95 to 3.15 in

Reproduction

The black-throated gray warbler is monogamous, as seen with one male mating with one female. The female is the primary nest builder. The male does not help in building the nest, but it does follow the female to and from the nest as she collects materials to signify his mating relationship with the female. The nests are typically located 0.91 to 9.75 meters from the ground. Nests are commonly found in shrubbery, but many have been spotted in high tree tops. The nests are constructed in an open cup shape, made from weeds, grass, and moss, and they are lined with fur and feathers.

The male black-throated gray warbler is known to have a mating song, while the female is not known to sing. The male's mating song consists of several short intervals of soft pitched 'zee' sounds to attract a mate. (Barlow, 1899; Chuang-Dobbs, et al., 2000; Dunn and Garret, 1963; Goodbred and Holmes, 1996; Stephenson and Whittle, 2013)

The black-throated gray warbler breeds seasonally from May to July and lays eggs from May to June. The females' sexual reproduction is oviparous with internal fertilization. There is little known on the courtship or nesting of the black-throated gray warbler. The female lays 3 to 5 eggs, but the typical brood consists of four eggs that average a mass of 1.3 grams. The eggs are described as "creamy white," with red specks that give them a pinkish color.

A typical hatchling weighs 1.4 g on average. Incubation period, time to fledging, and time to independence are not reported. The female reaches sexual maturation at approximately 1 year, while the male reaches sexual maturation in 2 years. (Barlow, 1899; Chuang-Dobbs, et al., 2000; Dunn and Garret, 1963; Stephenson and Whittle, 2013)

  • Breeding interval
    Black-throated gray warblers breed seasonally, with one brood per mating season.
  • Breeding season
    May through July, and late nests may occur in September.
  • Range eggs per season
    3 to 5
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    2 years

The female hatches the brood and protects it from predators. After hatching, both the male and female black-throated gray warbler feed the chicks. The brood is altricial and are born naked with very few patches of down feathers. After the chicks reach maturation, they remain in the nest with their mother for an unknown amount of time to protect them from predators. This shows a post-independence association with their mother. (Barlow, 1899; Chuang-Dobbs, et al., 2000; Goodbred and Holmes, 1996; Scott, et al., 2000)

Lifespan/Longevity

In the wild, this bird has been observed to live up to 11 years and as little as 7 years. The average lifespan is 8.5 years in the wild. The black-throated gray warbler has not been held in captivity. (Chuang-Dobbs, et al., 2000; Stokes and Stokes, 2004)

  • Range lifespan
    Status: wild
    7 to 11 years
  • Average lifespan
    Status: wild
    8 years

Behavior

The black-throated gray warbler is a social species that is commonly found in flocks with its own species during migration. It can also migrate with other bird species. It does not scare easily and can be approached while it is foraging.

This warbler is mobile and migratory. In the warm months of spring and summer (typically May-July, although can be as late as September) the black-throated gray warbler migrates from the western coast of Central America northward across the western coast of North America to southern British Colombia.

Their arboreal activity is often concentrated in the higher branches of mature tress, but they may nest within a meter of the ground. The black-throated gray warbler is diurnal. The male shows aggression to defend its territory by chasing away other males of its own species. (Barlow, 1899; Chuang-Dobbs, et al., 2000; Dunn and Garret, 1963; Gilfillan, 2010; Goodbred and Holmes, 1996; Morse, 1989; Rapai, 2012; Stephenson and Whittle, 2013; Stokes and Stokes, 2004; Thorton, 1999)

Home Range

There is not much information on the home range of the black-throated gray warbler. However, researchers report densities of 8.3 singing males per 100 hectares in logged forests and 9.6 singing males per 100 hectares in un-logged forests. (Barlow, 1899; Chuang-Dobbs, et al., 2000; Dunn and Garret, 1963; Goodbred and Holmes, 1996; Rapai, 2012; Stephenson and Whittle, 2013; Stokes and Stokes, 2004; Thorton, 1999)

Communication and Perception

The black-throated gray warbler has a high pitched song that contains many "zees". During breeding season the male is known to have a low-soft tune with short intervals between their notes. Male black-throated gray warblers sing in choruses or duets. This is a form of communication just before breeding season. During communication with other males, the black-throated gray warbler changes the tempo of its song. Male to male interactions, typically before breeding season, consist of rapid, high-pitched notes. The female black-throated gray warbler is not known to sing. Both the male and female black-throated gray warbler use visual cues such as wing flapping to communicate. The male is the only one with an acoustic means of communication. Both the male and female can use visual, tactile, acoustic, and chemical perception channels. (Dunn and Garret, 1963; Harrison, 1984)

Food Habits

The black-throated gray warbler is an insectivore that preys heavily on catepillars (notably the California oak worm Phryganidia californica). It mainly forages on the leaves of low-lying shrubs and the leaves of trees. Although, they mostly forage on the ground, or on shrubs close to the ground, they have been observed following flying insects and catching them in the air. They often forage in flocks. (Barlow, 1899; Bent, 1963; Curson and Quinn, 1994; Dunn and Garret, 1963; Gilfillan, 2010; Harrison, 1984; Martin, 1980; Stokes and Stokes, 2004; Stephenson and Whittle, 2013)

  • Animal Foods
  • insects

Predation

Cyanocitta cristata, the blue jay, is a predator of the black-throated gray warbler. If approached by a predator the black-throated gray warbler (more often, the female) will feign a broken wing and will skit around the nest until he or she is able to draw away the predator. The female black-throated gray warbler also has a warning call to alert her young of a potential predator. At the sound of this call, the chicks will fly from the nest and will later return when the predator is no longer in the area. (Goodbred and Holmes, 1996; Stephenson and Whittle, 2013)

Ecosystem Roles

The black-throated gray warbler is a known host for the protozoan, Trypanosoma brucei, which is known to cause African sleeping sickness. Hippobosca equina, the forest fly, is a noted ectoparasite of the black-throated gray warbler.

The brown-headed cowbird (Molothrus ater) is a known brood parasite of this warbler. (Guzy and Lowther, 2012; McClure, 1984; Wood and Herman, 1943)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known direct positive economic impacts of this warbler on humans. Because it is a migratory songbird, it's possible that it contributes to ecotourism through bird-watching activities. (Goodbred and Holmes, 1996; Morse, 1989; Rapai, 2012; Stokes and Stokes, 2004)

Economic Importance for Humans: Negative

The black-throated gray warbler has no known negative economic effects on humans. (Goodbred and Holmes, 1996; Rapai, 2012; Stokes and Stokes, 2004)

Conservation Status

The black-throated gray warbler is listed as protected under the US Migratory Bird Treaty Act. Under this act, this warbler and all other migratory birds cannot be "taken" in any way (traded, sold, hunted, or transported).

It has no special listing under the US Federal List, CITES, or the State of Michigan List. Under the IUCN Red List it is listed as "least concern."

Conservation measures are not currently in place. Research has shown that these birds can inhabit altered (logged) habitats in nearly the same densities as unlogged forest stands. No other studies have suggested that humans have impacted this species. However, long-term breeding and migration studies lack the sample size to adequately assess the status of this warbler. (BirdLife International, 2014)

Contributors

Ginger Frogel (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Genevieve Barnett (editor), Colorado State University.

Glossary

Nearctic

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

Neotropical

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

World Map

acoustic

uses sound to communicate

altricial

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.

arboreal

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. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

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

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

insectivore

An animal that eats mainly insects or spiders.

iteroparous

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).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

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.

oviparous

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

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

riparian

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

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

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

social

associates with others of its species; forms social groups.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

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).

terrestrial

Living on the ground.

tropical

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

visual

uses sight to communicate

References

Barlow, C. 1899. The nesting haunts of the black-throated gray warbler. Bulletin of the Cooper Ornithological Club, 1/5: 96-97.

Bent, A. 1963. Life Histories of North American Wood Warblers. New York: Dover.

BirdLife International, 2014. "The IUCN Red List of Threatened Species Version 2014.3" (On-line). Dendroica nigrescens. Accessed March 20, 2015 at http://www.iucnredlist.org/details/22721679/0.

Chuang-Dobbs, H., M. Webster, R. Holmes. 2000. The effectiveness of mate guarding by male black-throated blue warblers. Behavioral Ecology, 12/5: 541-546.

Curson, J., D. Quinn. 1994. New World Warblers. London: Christopher Helm.

Dunn, J., K. Garret. 1963. A Field Guide to Warblers of North America. Boston: Houghton Mifflin.

Gilfillan, M. 2010. The Warbler Road. Chicago: Flood Editions.

Goodbred, C., R. Holmes. 1996. Factors affecting food provisioning of nestling black-throated blue warblers. The Wilson Bulletin, 108/3: 467-469.

Guzy, M., P. Lowther. 2012. Black-throated Gray Warbler. Birds of North America (on-line), 319: 1.

Harrison, H. 1984. Wood Warblers' World. New York: Simon and Schuster.

Martin, C. 1980. Habitat selection in birds: The roles of vegetation structure, competitors, and productivity. BioScience, 31/2: 107-113.

McClure, H. 1984. The occurrence of hippoboscid flies on some species of birds in southern california. Journal of Field Orinthology, 55/2: 230-240.

Morse, D. 1989. American Warblers: An Ecological and Behavioral Perspective. Cambridge, Massachusetts: Harvard University Press.

Rapai, W. 2012. The Kirtland's Warbler: The Story of a Bird's Fight Against Extinction and the People Who Saved It. Ann Arbor, Michigan: University of Michigan Press.

Scott, T., R. Holmes, T. Sherry. 2000. Impacts of a global climate cycle on population dynamics of a migratory songbird. Science, 288/5473: 2040-2042.

Stephenson, T., S. Whittle. 2013. The Warbler Guide. New Jersey: Princeton University Press.

Stokes, D., L. Stokes. 2004. Stokes Field Guide to Warblers. Boston: Little Brown.

Thorton, B. 1999. Chasing Warblers. Austin, Texas: University of Texas Press.

Wood, S., C. Herman. 1943. The occurrence of blood parasites in birds from southwestern United States. The Journal of Parasitology, 29/3: 187-196.

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