Bullock's Oriole (Icterus bullockii) [XC177193]
by Richard E. Webster from Palomar Mountain, South Grade Rd, San Diego County, California, United States (call, song)
Bullock's Oriole (Icterus bullockii) [XC308762]
by Kent Livezey from Zapopan, Zapopan, Jalisco, Mexico (call)
Subspecies
Icterus galbula (Sibley and Monroe 1990, 1993) has been split into Northern Oriole (Icterus galbula), Bullock's Oriole (Icterus bullockiorum) and Black-backed Oriole (Icterus abeillei) following AOU (1998).
DNA data indicate that present species is sister to Streak-backed Oriole (Icterus pustulatus). In the past usually treated as conspecific with Northern Oriole (Icterus galbula) and Black-backed Oriole (Icterus abeillei). Hybridizes extensively with Northern Oriole (Icterus galbula) in a belt from southern Canada (Alberta and Saskatchewan) southern in Great Plains to southern USA (Oklahoma and Texas), but assortative mating (or selection against hybrids) evident at several locations. Smaller subspecies parvus possibly not worthy of recognition, and size difference within species apparently clinal; retained pending further study.
Proposed subspecies eleutherus (from northern Texas, in southern USA), supposedly more orange than nominate, considered to fall within range of variation of latter.
The following 2 subspecies are recognised:
bullockii (Swainson, 1827) - Breeds south-western Canada (from southern British Columbia, southern Alberta and south-western Saskatchewan) southern in western USA (except central California south to western Arizona) to northern Mexico (Sonora, Chihuahua and Coahuila). Winters central Mexico south to central Guatemala.
parvus van Rossem, 1945 - Breeds south-western USA (from central California, southern Nevada and western Arizona) south to north-western Mexico (extreme northern Baja California and extreme north-western Sonora); winter range uncertain.