Hermit Warbler, Setophaga occidentalis

Hermit Warbler, Setophaga occidentalis. Photograph taken within the Reserva Chara Pinta, El Palmito, Sinaloa, February 2019. Photograph and identification courtesy of David F Smith, Alamos, Sonora.

Hermit Warbler, Setophaga occidentalis. Photograph taken within a residential community in Hereford, Arizona, May 2010. Photograph and identification courtesy of Bob Behrstock, Sierra Vista, Arizona (naturewideimages.com).

The Hermit Warbler, Setophaga occidentalis, is a member of the Parulidae Family of New Wood Warblers, which has one hundred eleven species placed in eighteen genera and is one of thirty-four global species of the Setophaga Genus. They are named for their solitary and secretive behavior residing within the interior and canopy of tall coniferous forests. They are seldom seen and normally only located by their singing. They are known in Mexico as chipe cabeciamarillo.

The Hermit Warbler is a medium sized wood-warbler. Adult males have an almost entirely yellow head with a black chin, throat, upper breast, and nape with white underparts and gray upperparts with white wing-bars and tail-spots. The females are similar to the males but duller in color with olive green on the nape and throat, or absent on the throat, and white to light gray flanks. Their bill is horn colored, their iris is dark brown, and their legs and feet are horn colored with the undersides of their feet being yellow.

The Hermit Warbler is found within the canopy of pine-oak forest at elevations up to 3,300 m (10,800 feet). They forage in mixed flocks with their diets consisting primarily of invertebrates: beetles, true bugs, caterpillars, flies, spiders, stone flies, and wasps. They have a life span of up to four years. The Hermit Warbler in general, is very poorly studied and very little about their biology and behavioral patterns has been documented.

The Hermit Warbler summers and breeds within the coniferous forests of the Cascade, Coast, and Sierra Nevada mountains ranges of southern Washington, Oregon, and central and northern California. They are complete medium to long distance migrators that winter in the pine-oak and pine forests within the mountains of Mexico and Guatemala.

In Mexico the Hermit Warbler are found from Durango to the Jalapa Enríquez region of Nuevo León within the Central Volcanic Belt at elevations between 2,000 m (6,600 feet) and 3,300 m (10,800 feet) and south within the cloud forests of Oaxaca and Chiapas.

The adult Hermit Warbler is a straightforward identification due to their colorations. Adult females are similar to female Black-throated Green Warbler, Setophaga virens, (less gray underparts and less extensive yellow on the face), the female Golden-cheeked Warbler, Setophaga chrysoparia, (black streaking on the sides, dark forehead, black eye stripe), and the female Olive Warbler, Peucedramus taeniatus (white patch at the base of the primaries, more yellowish wash on the underparts, dark patch on ear-covert).

From a conservation perspective the Hermit Warbler is currently considered to be of Least Concern, with relatively stable, relatively widely distributed populations. There long-term viability is being threatened due to their small population size, limited distribution and by loss of their forested breeding and wintering habitats due to human development. There populations are also believed to be in decline due to out competition for available food supplies by the Townsend’s Warbler, Setophaga townsendi.