Illustration: Bronzed cowbird

Illustration by H. Douglas Pratt

Map

Map: Bronzed cowbird range

The largest of our cowbirds, the bronzed has a rather sinister appearance thanks to the male’s typically hunchbacked look and bloodred eye. It gives an odd hovering display that is unique. Polytypic. Length 8.7" (22 cm).

Identification A thick-set cowbird with a large and deep black bill. Males in particular may look proportionately small headed, especially when ruffling the nape feathers in display. Legs black. Adult male: entirely black with bronzed body iridescence, becoming blue-green on wings and tail. Eyes bright red. Adult female: varies geographically. More widespread eastern subspecies has a black female plumage, lacking strong gloss, with browner wings and tail. Eyes red. Juvenile: similar to female but dark brown.

Geographic Variation Four subspecies recognized, 2 in North America: the more widespread aeneus, found from south-central Texas eastward, and loyei from New Mexico to California. Males are similar, but females black in aeneus and grayish brown in loyei.

Similar Species The bronzed is larger than other cowbirds, and adults show bright red eyes and thick bills. Juveniles could be mistaken for female brown-headed cowbirds, but note their larger size, larger bulk, and thick bill. There is no blackbird with red eyes on the continent other than the very different Phainopepla, which is slim and crested, with white wing patches.

Voice Call: a rasping chuck. Females give a rattle. Song: a series of odd squeaky gurgles, gluup-gleeeep-gluup-bloooop. Flight whistle highly geographically variable, given in flight and while perched. About 4 seconds long, it is a series of long sliding or vibrating whistles. Three general dialects in North America: “Arizona” (California to westernmost Texas), “Big Bend” (Big Bend, Texas), and “South Texas” (east of Big Bend).

Status and Distribution Uncommon to fairly common. Year-round: open shrubland, forest edge, and agricultural areas (especially those associated with livestock). Breeding: brood parasite, specializes on sparrows and orioles. Migration: not well known. Spring movements in Texas in March, southbound movements in September. Small but increasing numbers winter in Florida. Winter: in flocks, particularly in agricultural areas. Vagrant: accidental in Nova Scotia, Missouri, and Maryland.

Population The range and population of this species began a marked expansion in the 1950s, but presently the population appears stable. It has recently spread to Florida and the Gulf states.

—From the National Geographic book Complete Birds of North America, 2006

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