Lucy's Warbler Life History

Habitat

Lucy’s Warblers are most common in dense mesquite woodlands (or “bosques”) of the southwestern United States, where they can reach up to 5 pairs per acre. These woodlands are most prevalent near streambeds. Lucy’s Warblers also breed (in lower densities) in stands of non-native tamarisk. Other common plants of such desert habitats include acacias, hackberries, and elderberries. In drier areas of scrub and grassland, Lucy’s sometimes nest in stands of willows, arrowweed, paloverde, and ironwood. They also occupy riparian cottonwood-mesquite forests and, at higher elevations, transitional woodlands with ash, walnut, sycamore, and oak. They normally occur below about 3,000 feet elevation, but some inhabit open woodlands of sycamore, alder, and oak up to 5,800 feet in central Arizona. After breeding, Lucy’s Warblers move to wetter habitats during the July–August monsoon (wet) season. Here they molt in preparation for migration. This phenomenon has not been the subject of much study, but such birds appear to utilize both grasslands and riparian areas at this time. Their wintering habitats in Mexico resemble breeding habitat, mostly riparian forest and thorn forest at lower elevations. Lucy’s Warblers sometimes winter in mesquite and tamarisk in the Big Bend region of Texas.

Food

Lucy’s Warblers eat mostly insects, which they capture by gleaning from leaves, branches, and bark. They often feed high in the small trees of their habitat, near the tips of branches and in flowers. Their small, light bodies perch easily on the thinnest of twigs, and they often hang upside down (like a Bushtit or chickadee) when searching for food. Lucy’s Warblers also catch insect prey on the ground. The few studies of their diet indicate that they eat small beetles (flower beetles, tiger beetles, ground beetles), caterpillars, bugs, leafhoppers, ants, bees, wasps, and spiders. Though they do probe tree blossoms, probably hunting small insects and spiders, they don’t seem to feed on nectar.

Nesting

Nest Placement

Nests are set in cavities and crevices of many kinds, usually less than 8 feet off the ground but sometimes up to 20 feet. The species uses woodpecker holes, bark gaps, old nests (of thrashers, Verdin, Cliff Swallow, etc.), streambed crevices, rock crevices, and even dense vine tangles.

Nest Description

The female builds a small cup nest of twigs, straw, grass, leaves, leaf stems, and flowers, lined with plant fibers, hair, bark strips, and feathers. Nests average about 3.4 inches across and 3 inches tall, with interior cup about 2 inches across and 1.7 inches deep.

Nesting Facts

Behavior

As soon as they return from wintering grounds in Mexico, male Lucy’s Warblers begin singing on territory. In prime habitat of dense mesquite with closed canopy, singing males can be a mere 100 feet apart, making it difficult to determine the size of territories. Along desert washes and creeks, where optimal breeding habitat is often confined to the immediate area of the streambed, Lucy’s Warblers defend linear territories of perhaps 600 feet. Males sing and patrol territory boundaries vigorously, frequently countersinging with other males at the borders. When a rival breaches the boundary, the territory holder may flick the tail, raise the crown feathers, and chip or sing loudly and rapidly before attacking. Males in courtship drop the wings to display their cinnamon rump patch and also raise the cinnamon crown feathers while singing and sometimes chasing females. Females build the nest, and both parents incubate eggs and feed young. After breeding, small family groups sometimes forage together.

Conservation

According to the North American Breeding Bird Survey, Lucy's Warbler populations were stable between 1968 and 2015. Partners in Flight estimates a global breeding population of 3 million and rates the species an 11 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Throughout its range, Lucy’s Warbler is threatened by the loss of riparian habitat, especially mesquite bosques, which hold much of the population. This species does nest at lower densities in tamarisk, an invasive exotic species that thrives in much the same geographic area as native mesquites. Some restoration projects have removed tamarisk and replanted native mesquites from such areas. Other birds of this habitat such as Yellow-billed Cuckoo, (Southwestern) Willow Flycatcher, and Yellow Warbler also benefit from such riparian restoration efforts.

Credits

Johnson, R. Roy, Helen K. Yard and Bryan T. Brown. (2012). Lucy's Warbler (Oreothlypis luciae), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

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

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. 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.

Stephenson, T. and S. Whittle (2013). The Warbler Guide. Princeton University Press, New Jersey, USA.

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