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California Gnatcatcher Life History

Habitat

Habitat Scrub

California Gnatcatchers live in coastal sage scrub, desert scrub, and coastal dune scrub year-round. In California they occur along the coast in areas dominated by California sagebrush. They generally occur in areas less than 1,600 feet in elevation, but sometimes occur at higher elevation at inland scrub sites. In Baja California, Mexico they occur in sparse desert woodlands, coastal dune scrub, and desert scrub. During the nonbreeding season, they may forage in chaparral areas especially if it borders sage scrub.

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Food

Food Insects

California Gnatcatchers pick insects from foliage or hover above shrubs to grab prey. Their diet includes leafhoppers, beetles, bugs, and spiders.

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Nesting

Nest Placement

Nest Shrub

Male California Gnatcatchers select a nest site in sagebrush, buckwheat, or other shrub species. The nest shrub is often on a gentle slope or within a gully or drainage. Within the shrub the nest is around 2.5 feet above the ground near the outer edge.

Nest Description

The male and female both build the nest, although the male does the majority of the work. The male brings pieces of bark, dried vegetation, and spiderweb to form a solid base, to which the female adds more material. The completed nest is a deep and sturdy cup around 2.5 inches wide and more than 2.5 inches deep.

Nesting Facts

Clutch Size:2-5 eggs
Number of Broods:1-2 broods
Egg Length:0.5-0.6 in (1.3-1.5 cm)
Egg Width:0.4-0.5 in (1.1-1.2 cm)
Incubation Period:14 days
Nestling Period:10-15 days
Egg Description:

White with small spots of reddish brown scattered throughout.

Condition at Hatching:

Naked with eyes closed.

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Behavior

Behavior Foliage Gleaner

California Gnatcatchers lightly flit through shrubs as if being blown by a breeze. They pick insects from sagebrush and other shrubs and never seem to slow down. Their kittenlike harsh meow often comes from deep inside a shrub, although males sometimes call from exposed perches while flicking their tail. California Gnatcatchers are monogamous and maintain pair bonds and territories year-round. Males chase intruding males and juveniles out of their territory, but often tolerate lone females. Paired females also take part in territory defense, chasing out juveniles and females, but rarely lone males. Female Brown-headed Cowbirds often lay an egg in the nests of California Gnatcatchers. The gnatcatcher eggs are either kicked out by the cowbird or are smothered by the much larger cowbird nestling. Parasitized nests very rarely fledge gnatcatcher young.

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Conservation

Conservation Restricted Range

California Gnatcatchers are uncommon. Partners in Flight gives them a Continental Concern Score of 14 out of 20, placing them on the Yellow Watch List for species with a declining population. The U.S. Fish and Wildlife Service lists the coastal California subspecies of California Gnatcatcher as Threatened under the Endangered Species Act. Partners in Flight estimates the global breeding population at 80,000 individuals. The U.S. Fish and Wildlife Service estimated in 1999 that there were 6,000 individuals in the United States. Since the mid-1940s suburban sprawl has drastically reduced and fragmented coastal sage scrub that California Gnatcatchers rely on. For example, in the United States 70–90% of gnatcatcher habitat has been lost. Conservation efforts have focused on establishing standardized monitoring protocols, trapping Brown-headed Cowbirds (which lay their eggs in gnatcatchers’ nests), and increasing research into the biology of California Gnatcatchers.

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Credits

Atwood, Jonathan L. and David R. Bontrager. (2001). California Gnatcatcher (Polioptila californica), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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