Hermit Warbler (Dendroica occidentalis)

Distribution

Breeding: Southwestern Washington south through Sierra Nevada of California and west-central Nevada, and south to central California coastal mountains. Populations are fragmented within the range. Hybrid zone with Townsend’s Warbler in area of overlap in Oregon and Washington.

Winter: Primarily in Mexico and Central America, from Durango and southern Nuevo Leon south through Oaxaca and Chiapas to Guatemala, and southern Honduras to western Nicaragua. Rare and local in coastal central and southern California and in west-central Nicaragua and Costa Rica; accidental to western Panama. Highest densities occur in Central Volcanic Belt of Mexico.

Breeding habitat

Pacific northwestern coniferous forests with a high canopy volume, generally preferring mature stands of pine and Douglas fir. Douglas fir is an important tree species throughout the breeding range, also found in lower densities in subalpine forests dominated by subalpine fir, lodgepole pine, and other conifers. In the California mountains, found in forests of red and white fir, sugar, Ponderosa, Jeffrey, and lodgepole pine, and giant sequoia. Avoids areas with a high deciduous volume; absent from riparian areas and clearcuts.

Conservation status

This species is of high conservation importance, because of its small overall distribution and association with mature coniferous forests in the Pacific Northwest. Although somewhat tolerant of second-growth forests, the Hermit Warbler is vulnerable to largescale forest clearing. Its precise habitat requirements and sensitivity to forest fragmentation throughout its range are poorly known. Populations are poorly monitored, but appear to be stable at present.

Description

Male: Bright yellow on face, crown, and cheek patch, variable black on nape, otherwise grayish or olive-gray upperparts spotted with black. Throat and chin black, underparts white with limited streaking (or absent) on flanks, two prominent white wing bars.

Female: A dingier version of the male, cheek has a dark tinge, variable black spotting on crown. Black on throat is limited, sometimes absent, sometimes extensive but not including chin. White wing bars prominent.

Juvenile: Head and upperparts olive-brown, only a hint of streaking, cheek area darker than adults. Throat and breast are grayish-brown, belly white.

Hybrids: Hermit x Townsend’s Warblers occur regularly in Oregon and Washington. Hybrids typically show head pattern of Hermits with Townsend’s body coloring (some yellow on the breast below the black throat and streaking on the flanks). More rarely, hybrids may show the face pattern of the Townsend’s with the coloring of a Hermit’s body (no yellow on the breast and only limited streaking on the sides).

Vocalizations

Songs: Only male sings. Two distinct song types, but exact pattern extremely variable.

First-category songs dominate singing early in breeding season, before males are mated, and decline after pairing. They typically consist of 4 high-pitched notes, che che che che, followed by a descending phrase, cheeo, then a rapid series of buzzy notes, ze ze ze ze ze ze, and a final high-pitched note, ZEET.

Second-category song dominates after pairing and typically consists of 3 or 4 doubled, buzzy notes, zeegle zeegle zeegle; followed by rising-and-falling ending phrase, zee-o-seet.

Calls: A flat chip or tip, nearly indistinguishable from that of Townsend’s and Black-throated Green warblers. Both male and female give the chip note.

Foraging strategy

Moves through canopy and sub-canopy gleaning insect prey from foliage in middle and outer portion of tree branches. While foliage-gleaning is the primary strategy, hover-gleaning, lunging, and sallying for aerial prey are occasionally exhibited. Usually forages alone, although members of pair occasionally forage together.

Diet

Primarily invertebrates, including small spiders, caterpillars, beetles, flies, wasps, stone flies, and true bugs.

Behavior and displays

• Movement within foliage is mostly by hopping, but flies within or between trees. Direct flight consists of rapid short wing-beats and occasional short glides.

• Hover flight is used in conflict with other males or while gleaning food off branches.

• Breeding male spends much of the morning singing from high perches in favorable weather conditions and in the subcanopy under rainy conditions.

Courtship

• No information.

Nesting

Nest Site: Nests in older second-growth and mature forests, typically saddling the nest on the upper surface of a conifer branch, preferring pine, cedar, and Douglas fir. Often nests in trees that are well over 165 feet (50 meters) tall, placing the nest on a limb 13 feet (4 meters) out from the trunk. One exceptional nest was located on the ground at the base of a shrub.

Height: Average height is 23 feet (7 meters) above ground.

Nest: Females have been observed carrying nesting material, but no bird has been observed building a nest. The cup-shaped nest is constructed from fine twigs, rootlets, dry moss, bark (especially from cedar), pine needles, and spider silk; lined with fine plant fibers, hair, feathers, and down from cottonwood trees.

Eggs: 3–5 creamy white eggs are finely speckled and spotted with chestnut and auburn with intermingling spots of light brownish drab.

Incubation period: Little known, young hatch about day 12.

Nestling period: Nestlings are altricial and downy. Male and female both tend to the young at equal rates, with caterpillars the main food item.

Fledgling period: Little known, but in 1 nest observed on day of fledging, all young were within 10 feet (3 meters) of each other in the shrub layer directly below nest. The following day, the young were in the canopy approximately 32–50 feet (10–15 meters) above ground in 2 adjacent trees on natal territory, and both adults were feeding. Adults split broods within a few days of fledging; 1–2 young go with each parent. Within 2 days the young were capable of following adults through canopy.

Broods: No information.

Cowbird Parasitism: A rare host of the Brown-headed Cowbird.

Notes

• Male guards female closely during egg-laying, presumably as strategy to avoid extra-pair copulation.