Hermit Warbler Life History

Habitat

Habitat Forests

In spring and summer, Hermit Warblers inhabit coniferous forests in mountainous areas, especially where tree canopies are well developed rather than open. In the Coast, Cascade, and Sierra Nevada ranges of the Pacific coastal states, Hermit Warblers occur in forests of sugar, lodgepole, Jeffrey, western white, and ponderosa pines, subalpine, red, and noble firs, incense-cedar, Douglas-fir, coast redwood, and giant sequoia. Such forests may have understory with deciduous trees and various shrub cover, but neither are necessary for Hermit Warblers, which remain mostly in the upper portion of tall trees in forests with closed canopies. They are scarce or absent in forests of western hemlock, mountain hemlock, or western redcedar. Migrating Hermit Warblers show up in many different habitats, including tall coniferous woodlands similar to breeding habitat but also in pine-oak and oak woodlands, and even in lowland riparian woodlands, parks, orchards, and desert oases. Wintering birds in California use oak and pine woodlands and parks, but in Mexico and Central America most winter in high elevations from about 4,000 feet to 11,000 feet elevation, in pine, pine-oak, and cloud forest.

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Food

Food Insects

Hermit Warblers eat mostly insects and spiders. They forage in tree canopies, with males often foraging higher than females. Both sexes forage most actively in the morning and the late afternoon. They move quickly through the canopy, picking insects from branches and foliage while hopping or walking, sometimes hovering to grab an insect but rarely pursuing prey in flight. Their diet includes moths, butterflies, caterpillars, beetles, flies, wasps, stone flies, bugs, and spiders; they also eat small amounts of fruit, especially in the winter. Like other small songbirds, they eat "honeydew," a sugar-rich excretion of scale insects and aphids. In Mexico, both Yellow-rumped and Townsend’s Warblers chase Hermit Warblers away from honeydew-rich trees.

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Nesting

Nest Placement

Nest Tree

Nests are set on a horizontal limb high above ground and usually well hidden by foliage.

Nest Description

The female probably constructs the nest on her own, a cup of twigs, roots, moss, bark, and pine needles lined with fine plant fibers, hair, feathers, and plant down, fastened together with spiderweb. Nests average about 3.9 inches across and 2.1 inches tall, with interior cup 2 inches across and 1.2 inches deep.

Nesting Facts

Clutch Size:4-5 eggs
Egg Description:

Creamy white with fine dark speckles around large end.

Condition at Hatching:

Helpless with tufts of down.

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Behavior

Behavior Foliage Gleaner

Hermit Warblers breed in beautiful but often remote areas, and their tendency to stay high in the canopy means that their breeding behaviors, including courtship, are almost unknown. Males remain close to females until egg-laying, often foraging close to their mates, but otherwise Hermit Warblers appear to forage alone in summer. Both sexes respond aggressively to intruders of their species in their territory. Both male and female share incubation and chick-feeding duties, and the fledged young forage with the adults after leaving the nest, sometimes in association with other songbirds. During migration, and especially on the wintering grounds, Hermit Warblers travel and forage with large mixed-species flocks of woodpeckers, woodcreepers, flycatchers, warblers, vireos, tanagers, and other woodland species.

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Conservation

Conservation Low Concern

According to the North American Breeding Bird Survey, Hermit Warbler populations were stable between 1968 and 2015. Partners in Flight estimates a global breeding population of 2.5 million and rates the species a 12 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Loss of habitat, particularly on the wintering grounds, is the chief concern for Hermit Warblers, since they have fairly specialized habitats and a relatively small range. Some scientists have raised the concern that Townsend’s Warblers, which are less specialized in their habitat requirements, have been outcompeting Hermit Warblers not just in the hybrid zone but in areas formerly occupied only by Hermit Warblers.

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Credits

Lutmerding, J. A. and A. S. Love. (2019). Longevity records of North American birds. Version 1019 Patuxent Wildlife Research Center, Bird Banding Laboratory 2019.

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

Pearson, S. F. (2000). Behavioral asymmetries in a moving hybrid zone. Behavioral Ecology 11 (1):84-92.

Pearson, Scott F. (2013). Hermit Warbler (Setophaga occidentalis), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Rohwer, S. and C. Wood. (1998). Three hybrid zones between Hermit and Townsend's Warblers in Washington and Oregon. Auk 115 (2):284-310.

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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