Giant Cowbird
Molothrus oryzivorus
Rather large blackbird of tropical lowlands; male is much larger than female. Found in forest edges, pastures, orchards, and open grassy areas along rivers; often in small groups. In breeding season, hangs around oropendola colonies, where it lays its eggs in oropendola nests and relies on them to raise its offspring. Thick neck accentuates small head with very stout, pointed bill. Flight is strong and fairly direct, with distinctive flap-flap-flap-glide progression. Eye color varies: red in Mexico and Central America, yellowish in parts of South America.
Identification
The male giant cowbird is 34 cm (13 in) long, weighs 174–242 g (6.1–8.5 oz) and is iridescent black, with a long tail, long bill, small head, and a neck ruff which is expanded in display. The female is smaller, averaging 29 cm (11 in) in length and weighing 144–167 g (5.1–5.9 oz). The female is less iridescent than the male, and the absence of the neck ruff makes her look less small-headed. Juvenile males are similar to the adult male, but browner, and with a pale, not black, bill.<p>It is a quiet bird, particularly for an icterid, but the male has an unpleasant screeched whistle, shweeaa-tpic-tpic. The call is a sharp chek-chik. They are also very adept mimics.
Taxonomy
The giant cowbird was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the orioles in the genus Oriolus and coined the binomial name Oriolus oryzivorus. Gmelin based his account on the "rice bird" from Cayenne that had been described in 1782 by the English ornithologist John Latham in his multi-volume work A General Synopsis of Birds. The specific epithet is from Latin oryza meaning "rice" and -vorus meaning "eating". The giant cowbird is now one of six cowbirds placed in the genus Molothrus that was introduced in 1832 by William Swainson.<p>Two subspecies are recognised:
- Scientific name
- Molothrus oryzivorus
- Authority
- (Gmelin, JF, 1788)
- Order
- Passeriformes
- Family
- Icteridae
- Genus
- Molothrus
Range and habitat
It is associated with open woodland and cultivation with large trees, but is also the only cowbird that is found in deep forest.
- Migration
- Resident species
Behavior
Like other cowbirds, it is a brood parasite, laying its eggs in the nests of oropendolas and caciques. The eggs are of two types, either whitish and unspotted, or pale blue or green with dark spots and blotches. The host's eggs and chicks are not destroyed. Their icterid hosts breed colonially, and defend their nests vigorously, so even a large, bold and aggressive species like the giant cowbird has to cover an extensive territory to find sufficient egg-laying opportunities. Several giant cowbird eggs may be laid in one host nest.<p>This gregarious bird feeds mainly on insects, and some seeds, including rice, and forages on the ground or in trees. It also searches for fruit, nectar, and arthropods along lakes and rivers, and in banana plantations and corn. It rarely perches on cattle, unlike some of its relatives, but in Brazil it will ride on capybaras as it removes ticks and/or horse flies.
Conservation
- Population trend
- declining
Photos
Distribution
Bird Calls
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