Black-tailed Gnatcatcher Life History

Habitat

Habitat ScrubBlack-tailed Gnatcatchers live year-round in semiarid and desert thorn scrub at elevations up to 7,000 feet, often among creosote bush, salt bush, mesquite, palo verde, ocotillo, and spiny hackberry, as well as cacti such as saguaro, prickly pear, cholla, and barrel cactus. Along the lower Colorado River they may use willows as well as the invasive species tamarisk (salt cedar). They are well adapted to dry habitats and tend to be most common in areas with less than 8 inches of annual rainfall. They often live far away from streams and other bodies of water. Back to top

Food

Food InsectsBlack-tailed Gnatcatchers eat almost entirely insects, occasionally supplemented with fruit or seeds. They forage energetically amid the thorns and leaves of shrubs, gleaning a wide variety of insects including caterpillars, walking sticks, beetles, ants, flies, bugs, grasshoppers, spiders, and insect eggs. Sometimes subdues larger prey by beating them against a branch. Back to top

Nesting

Nest Placement

Nest ShrubNests are placed in forks of branches in dense thorny or leafy trees or shrubs, with plenty of vegetation overhead and around the sides to shield the nest from the hot desert sun.

Nest Description

Black-tailed Gnatcatchers build a deep, compact cup out of woody fibers, which they line with plant down, cactus wool, spiderweb, feather, or fur. Both sexes work on building the nest, a process that takes 2–4 days.

Nesting Facts
Clutch Size:3-5 eggs
Number of Broods:1-2 broods
Egg Length:4.7-5.9 in (12-15 cm)
Egg Width:3.9-4.7 in (10-12 cm)
Incubation Period:14-15 days
Nestling Period:9-15 days
Egg Description:Pale-white to pale-blue, variably speckled in red.
Condition at Hatching:Born naked, blind, and helpless.
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Behavior

Behavior Foliage GleanerBlack-tailed Gnatcatchers hop quickly from branch to branch as they search for insects on leaves and branchlets, with a near-constant flicking of the tail both up and down and from side to side. They move from shrub to shrub in short bursts of undulating flight. Black-tailed Gnatcatchers form monogamous pair bonds, and pairs often remain together year-round defending permanent territories. Once the breeding season has ended, they sometimes forage in loose groups and even roost together at night to stay warm. Their nests are frequently parasitized by much larger Brown-headed Cowbirds. These small birds don’t hesitate to attack larger birds (including Cactus Wrens, Curve-billed Thrashers, Canyon Towhees, Northern Mockingbirds, Pyrrhuloxias, and Brown-headed Cowbirds) that get too close to their nests. Where their range overlaps with California Gnatcatcher, the two species defend territories against each other.Back to top

Conservation

Conservation Low ConcernBlack-tailed Gnatcatchers are numerous, but their populations decline. Partners in Flight estimates the global breeding population at 15 million individuals, with 30% in the U.S. and 70% in Mexico. They are a U.S.-Canada Stewardship Species and rate a 10 out of 20 on the Continental Concern Score. They are not on the 2014 State of the Birds Watch List. Black-tailed Gnatcatchers show low tolerance for disturbance: they typically nest only in native vegetation, don’t occur in areas with exotic or introduced plants, and are substantially less common in urban areas than in undeveloped areas. Back to top

Backyard Tips

Black-tailed Gnatcatchers don’t visit feeders or nest in boxes. The best way to attract them to your property is by hosting native trees and shrubs, such as creosote bush, salt bush, and mesquite. You can find more planting tips for your region at the Cornell Lab's citizen science project, YardMap.

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Credits

Farquhar, C. Craig and Karen L. Ritchie. 2002. Black-tailed Gnatcatcher (Polioptila melanura), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, 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, USA.

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