Polioptila melanurablack-tailed gnatcatcher

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Geographic Range

Black-Tailed Gnatcatchers are found throughout northern and central Mexico and the southwest deserts of the US. (Sibley 2000)

Habitat

All gnatcatchers are found in open areas. Black-Tailed Gnatcatchers prefer arid scrublands. They are common in desert washes. (Sibley et al 2001)

Physical Description

Black-Tailed Gnatcatchers are small blue-gray birds with a slender bill and tail. They are very active. The breeding male has a black cap which is not present in the basic plumage. Both males and females have a tail that is mostly black, with a small amount of white at the ends of the outer retrices. (Sibley 2000)

  • Average mass
    5 g
    0.18 oz
  • Average length
    11.4 cm
    4.49 in
  • Average wingspan
    14 cm
    5.51 in

Reproduction

It is thought that Black-tailed Gnatcatchers form monogomous pair bonds that last longer than the breeding season, but the duration of these bonds is not well known.

Black-Tailed Gnatcatchers form monogamous pair bonds for a given breeding season. The male defends a foraging territory. Numbers given for "number of offspring/eggs per season" are per nest. Double clutching is possible.

  • Range eggs per season
    2 to 6
  • Range time to hatching
    11 to 15 days
  • Range fledging age
    10 to 15 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Both sexes perform nest-building, incubate, and feed during the nestling and fledgling stages. It is common for the parents to raise a second brood shortly after the first. Black-tailed Gnatcatcher chicks are altricial. (Sibley et al 2001, Smith 1967)

Behavior

Black-tailed Gnatcatchers are active year-round throughout the desert regions they inhabit. They are less physically active during the summer, but they still may be observed foraging during the hottest periods in shady regions with a cooler microclimate.

They are not philopatric with respect to breeding grounds. When they are not breeding, they tend to wander throughout a region.

Black-tailed Gnatcatchers will dive-bomb another bird that approaches too close to an active nest. (Smith 1967)

Communication and Perception

Food Habits

In general, gnatcatchers feed by gleaning insects from the tips of branches. They mostly do this while perched; however, they are observed to do this while hovering near the branch tips as well. They also eat spiders. They occasionally catch insects in flight by making forays into the air from a perch. Collected specimens have been found with vegetable matter in the stomach, but this must account for only a tiny proportion of food eaten. Black-tailed Gnatcatchers obtain all of their water from the food they eat. (Sibley et al 2001, Smith 1967)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods

Ecosystem Roles

Black-tailed Gnatcatchers may be heavily parasitized by Cowbirds in some regions. (Smith 1967)

Economic Importance for Humans: Positive

None known.

Economic Importance for Humans: Negative

None known.

Conservation Status

Contributors

Hanna Coy (author), University of Arizona, Jay Taylor (editor), University of Arizona.

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

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.

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

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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.

internal fertilization

fertilization takes place within the female's body

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.

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

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.

territorial

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

visual

uses sight to communicate

References

Elphick, C., J. Dunning, D. Sibley. 2001. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf, Inc..

Sibley, D. 2000. The Sibley Guide to Birds. New York: Alfred A. Knopf, Inc..

Smith, E. 1967. Behavioral Adaptations Related to Water Retention in the Black-tailed Gnatcatcher (*Polioptila melanura*). University of Arizona: Unpublished M.S. Thesis.