Black-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
Black-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
Nests 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.
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.
|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.|
Black-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
Black-tailed Gnatcatchers are numerous, and their population held steady between 1968 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 11 million individuals and rates them 9 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. However, on the California coast, their numbers have dropped precipitously and they have a 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
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. (2020). Avian Conservation Assessment Database, version 2020.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.