Cardellina pusilla

Formerly placed in the genus Wilsonia. Phylogenetic analyses of sequences of nuclear and mitochondrial DNA (Lovette et al. 2010) indicate that two species formerly placed in the genus Wilsonia (canadensis and pusilla)and both species formerly placed in the genus Ergaticus (rubra and versicolor) form a clade with Cardellina rubrifrons. The generic name Cardellina has priority for this clade (AOU 2011).

Large breeding range in North America; large winter range mostly in Mexico and Central America; large population size; many occurrences; overall population apparently has declined over the past several decades, probably as a result of anthropogenic habitat changes.

Breeding range extends from most of Alaska eastward across central Canada to Labrador and Newfoundland, and south to southern Alaska, southern California, Nevada, Utah, northern New Mexico, central Saskatchewan, southern Manitoba, northern Great Lakes region, northeastern New York, northern Vermont, central Maine, and Nova Scotia (AOU 1998).

Primary winter range extends from coastal California (rare), southern Baja California, southern Sonora, southern Texas, southern Louisiana, southern Mississippi (rare), southern Alabama (rare), and Florida south through Middle America (rarely in the Yucatan Peninsula) to Panama (AOU 1998).

This species is represented by a large number of occurrences.

Population trends appear to be driven primarily by habitat changes. Ammon and Gilbert (1999) stated that population increases in northern forested regions in the 1960s and1970s may have been related to increased availability of midsuccessional, deciduous scrub habitats following logging, whereas regional decreases, particularly in the west, most likely reflect extensive destruction of riparian habitats. No other major threats have been identified, but the role of brood parasitism by brown-headed cowbird needs further study. Habitat changes in the winter range are not thought to be a significant concern at the present time (Ammon and Gilbert 1999).