Family Vireos (Vireonidae)

Least Concern

Cassin's Vireo (Vireo cassinii)


French: Viréo de Cassin German: Cassinvireo Spanish: Vireo de Cassin

Vireo cassinii


, 1858,

Fort Tejon, California, USA


Genetic data#R indicate that this species forms a group with V. plumbeus and V. solitarius; the three were formerly treated as conspecific, but molecular studies indicate that they merit treatment as separate species. Breeding range in W Canada overlaps slightly with that of V. solitarius, and some interbreeding may occur; cytochrome b sequence studies, however, indicate as much divergence between the two as between V. solitarius and V. flavifrons. Two subspecies recognized.

Subspecies and Distribution
  • V. c. cassinii Xántus, 1858 – SW Canada (S British Columbia S from c. 53° N, SW Alberta) and W USA (Washington and W Montana S to S California), disjunctly also in NW Mexico (mountains of N Baja California); migrates to S California (rare) and Arizona S to W Mexico (S to Oaxaca).
  • V. c. lucasanus Brewster, 1891 – S Baja California (NW Mexico).
  • Descriptive notes

    13·5–14 cm; 10–20·6 g. Nominate race has eyering and area above lores white ("spectacles" on face), crown to nape and upper back dull... read more


    Primary song, by male alone, a series of disjointed phrases, each consisting of 2–4 burry... read more


    Nominate race breeds in various forest types, including coniferous, deciduous and mixed stands;... read more

    Food and feeding

    In breeding season bulk of prey arthropods, especially caterpillars (Lepidoptera), bugs (Hemiptera) and treehoppers (Membracidae), beetles... read more


    Egg-laying starts late Apr in S to third week of Jun in N, later in interior locations than at coastal ones; no information on sedentary... read more


    S Baja California race (lucasanus) sedentary. Nominate race wholly migratory, with... read more

    Status and conservation

    Not globally threatened. Common. Over much of its range present in substantial densities, with quoted figures of up to as many as 13·7 pairs/40 ha in lightly thinned forest... read more

    Recommended citation

    Brewer, D. (2019). Cassin's Vireo (Vireo cassinii). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 25 April 2019).