Wilson’s Warbler, Cardellina pusilla

Wilson’s Warbler, Cardellina pusilla chryseola, Males. Photographs courtesy of Dr. Tom Bartol, Carlsbad, California, taken within the Organ Pipe Cactus National Monument in Southern Arizona, March 2018.

Wilson’s Warbler, Cardellina pusilla chryseola, Male. Photograph taken within a residential community in Alamos, Sonora, February 2019. Photograph and identification courtesy of David F Smith, Alamos, Sonora.

Wilson’s Warbler, Cardellina pusilla chryseola, Male. Photograph taken within a residential community in Hereford, Arizona, April 2011. Photograph and identification courtesy of Bob Behrstock, Sierra Vista, Arizona (naturewideimages.com).

Wilson’s Warbler, Cardellina pusilla chryseola, is one of three subspecies of Wilson’s Warbler that is a small member of the Parulidae Family of New World Warblers, which has one hundred eleven individual species that have been placed into eighteen genera and one of five global members of the Cardellina Genus. They are known in Mexico as reinita de Wilson.

The adult male plumage has upperparts uniformly yellowish olive green; forehead, supercilium, lores, and entire underparts lemon yellow, and crown glossy black forming prominent, well defined patch or cap on top of head. They do not have wing-bars or tail spots. Their black eye stands out conspicuously on their yellow face. The adult females are similar but duller overall with crown that is highly variable-may be entirely olive, black but heavily mottled with olive feathers, black with few to many olive feather tips, or uniformly black. The black crown patch, if present, is smaller in females than in males. Their bill is black or dusky brown and relatively short and wide with well-developed rictal bristles, their iris is dark brown to black, and their legs and feet are light brown, yellowish brown, dusky or horn-colored in adults and pinkish in juveniles. They are found in a wide variety of habitats ranging from coastal lowlands into high-altitude cloud forest; also, the only migrant that regularly occupies paramo (high-altitudes plains). They are terrestrial forages consuming terrestrial invertebrates and seasonal berries. They are known for their frequent lateral tail-flicking, tail-waving, rapid body movements, and fluttering in mid-air while hawking insects. Their life spans are greater than five years.

In Mexico Wilson’s Warbler are found at all elevations throughout the northern portions of the country on a year round basis; in the southern portion they medium to long distance migrants that winter during the months of December, January and February. The chryseola subspecies is found within the Pacific Slope in Western Mexico in Baja California Sur and from Southern Sonora south to Guatemala.

From a conservation perspective Wilson’s Warbler is currently considered to be of Least Concern with stable, widely distributed populations. Currently their populations are thought to be in decline which is attributed to large-scale destruction of riparian habitat and is some regions have been significantly adversely affected by herbicide applications.