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Polioptila caeruleablue-grey gnatcatcher

By Jennifer Roof

Geographic Range

The Blue-gray Gnatcatcher ranges over most of the United States east of the Mississippi, excluding Maine. It can also be found throughout Mexico, Cuba, Texas, Oklahoma, Nevada, Utah, and New Mexico. During the winter, gnatcatchers migrate to Central and South America.

Habitat

Gnatcatchers enjoy a wide range of woodland habitats, from shrublands to mature forests. They tend to avoid coniferous forests and concentrate largely along habitat edges. Some of their habitats include floodplain forests, lakeside habitats, pinyon-juniper woodlands, and arid, subtropical shrubbery.

Physical Description

Blue-gray Gnatcatchers are small birds, with a comparatively long tails. They are bluish-grey above and white below. The color of the bases of the wings blends into the black coloring at the tips. The tail is black with white streaks interspersed. There are prominent thin white rings around each eye.

  • Average mass
    6.5 g
    0.23 oz
    AnAge

Reproduction

Monogamous pairs are formed shortly after the return to the breeding range, in late March or April. There is no evidence as to whether these pairs are lifelong or if new pairs are formed every breeding season. The Gnatctacher nests fairly early for a North American songbird, sometime in the month of April. The nest is built by both the male and female, and takes nearly two weeks to complete. Three to five eggs are layed 5-10 days after construction is finished. The male and female both incubate. After another two weeks the young hatch. Both parents bring food to the young. Although both the male and female contribute to the care of the eggs and hatchlings, they do not interact with one another after incubation begins, seeing each other only in passing. They often fledge a second brood together later in the season.

  • Average eggs per season
    4
    AnAge
  • Average time to hatching
    13 days
    AnAge

Lifespan/Longevity

Behavior

With short mothlike flights, the Blue-gray Gnatcatcher prefers to hop from place to place, either on the groung or along branches. Aggressive behaviors include posturing with the tail raised and audible bill clapping. Gnatcatchers are territorial, displaying these actions toward same-sex intruders. Parents often attack fledglings from the first brood of the summer if they interfere with the rearing of the second brood.

Communication and Perception

Food Habits

Gnatcatchers eat mainly small insects and spiders. They search for food by moving up and down through the outer branches of trees or shrubs. Their preferred foods are (in order from highest amount to lowest): Homoptera (cicadas, aphids), Hemiptera, Coleoptera (beetles), Lepidoptera (mothsl, butterflies), Diptera (flies), Hymenoptera (ants, bees, wasps), and Araneae (spiders).

Conservation Status

Gnatcatchers have no special status; however, few data have been collected on the effects of human activity on their populations. Their numbers seem to be rising, indicating that subtropical deforestation is having little effect on these birds, which winter throughout shrub-based habitats in Mexico. Management may be needed for microhabitats in the U.S. (such as stream valleys and canopy openings), rather than large areas.

Other Comments

Gnatcatchers are migratory, with no distinctions in migratory schedules based on age or sex. They leave there wintering sites by mid-March. They remain at their breeding site until shortly after the young have become fully independent, usually in mid-August.

Contributors

Jennifer Roof (author), University of Michigan-Ann Arbor.

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.

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Neotropical

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

World Map

acoustic

uses sound to communicate

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.

chemical

uses smells or other chemicals to communicate

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.

forest

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

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).

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.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

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

tactile

uses touch to communicate

visual

uses sight to communicate

References

Ellison, Walter G. 1992. The Birds of North America. No. 23. The American Ornithologists' Union.

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