All species › Passerines › New World blackbirds › Giant Cowbird
Giant Cowbird | Molothrus oryzivorus
Grote koevogel | Tordo gigante
The Giant Cowbird is a brood parasite of oropendolas and caciques: the female lays her eggs in the hanging nests of these colonial birds. In the Caribbean it occurs only in Trinidad and Tobago. It probably colonised Tobago fairly recently.
Voice
Fairly quiet for an icterid. The male gives a penetrating, grating whistle and sharp, rasping calls, as well as chirping and clicking notes. It can mimic other sounds.
Recording: Paul Molina Abril — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
29–34 cm; the male is clearly larger than the female. Long wings, a fairly long tail and a small head. The male is glossy purple-black, with a neck ruff that is raised in display and makes the head look even smaller; the iris of adult males is red to orange. The female is smaller, duller brownish black and lacks an obvious ruff. The bill is black and pointed. Juveniles have a pale bill. In flight the long wings and an undulating flight stand out, a few wingbeats alternating with a short glide.
Confusion species
Carib Grackle Quiscalus lugubris is smaller and slimmer, with a yellow iris and a keel-shaped tail. Shiny Cowbird Molothrus bonariensis is much smaller, with a short, conical bill and no ruff. Smooth-billed Ani Crotophaga ani has a high, laterally flattened bill and a long, loose tail.
Habitat
Forest edge, clearings with tall trees, plantations, pastures and river banks in the lowlands, especially near colonies of Crested Oropendola and Yellow-rumped Cacique. It feeds on the ground on seeds, fruit and invertebrates, also among cattle. The female visits the hosts' colonies to lay; the host's eggs and young are not destroyed.
Where the bird is most at home, classified by the vegetation types of the Caribbean.
Range and movements
Resident in Trinidad, scattered through the lowlands, and in Tobago, where it is common. A vagrant to Barbados. Outside the region from southern Mexico through Central America to northern Argentina.
- Resident
- dark = core range, pale = thinly spread
How and when to look
Best looked for at oropendola and cacique colonies, where females wait quietly in the canopy for a chance to visit a nest. In open country the small head and long wings stand out; small groups also sit along roads and in pastures.
Conservation status
Not threatened. It is fairly common over much of its range and benefits where forest gives way to open country with scattered trees, as long as host colonies remain.
Scientific name
Molothrus oryzivorus | (Gmelin, 1788)
Gmelin described the species in 1788 as O[riolus] oryzivorus; because it was later moved to another genus, the author and year stand in brackets. The genus Molothrus was introduced in 1832 by Swainson. Molothrus is Greek, from mōlos 'struggle' and thrōskō 'to impregnate', perhaps after the brood parasitism or the males' courtship contests. oryzivorus is Latin, from oryza 'rice' and -vorus '-eating': 'rice-eater'. The specimen the first description was based on came from Cayenne, French Guiana.