Giant Cowbird

How to find it

Start with oropendola colonies. They are often in open trees beside roads, so you can pull over and scan them for cowbirds perched nearby. Watch the tops of trees holding nests, because the cowbirds hang around waiting for a chance to slip into an unguarded nest. Look also for it walking on the ground in pastures, farms, fields, wet areas and forest edges. It often visits feeders on farms and can be seen perched on cattle.

How to recognise it

The male is large and glossy purplish black. A ruff of neck feathers makes his head look small, and the iris is red to yellow. Males are about 33 to 37 cm long.

The female is smaller, about 28 to 32 cm, and a duller black. She lacks the neck ruff, so her head looks less small.

Both sexes have long pointed wings and a fairly long tail with a nearly square end.

Young birds are duller and sootier black, with a pale ivory-yellow bill and a yellow or brown eye.

What it sounds like

Recording: Niels Krabbe, CC BY-SA 4.0, source, read 5 Nov 2026.

Behaviour and diet

The Giant Cowbird is a brood parasite. It lays eggs in the nests of oropendolas and caciques, which are large colonial nesters.

It eats fruit, nectar and arthropods, and one bird had eaten rice.

It flies in a distinctive undulating way and is often seen walking on the ground, alone or in small groups. At Santa Rosa, in Guanacaste, a birder photographed cowbirds perched near Montezuma Oropendola nests being built.

Where it lives

Across its range it likes partly open country with scattered trees, farmland, second growth and plantations. It is usually near colonies of oropendolas or caciques, in the tropical and lower subtropical zones.

In Costa Rica it is recorded up to about 1700 m. It occurs on the Caribbean slope, the central plateau and the Pacific slope in the Golfo Dulce region. A photo labelled Vaquero Grande was taken at Boca Tapada, in the north.

Similar birds

It is only a little smaller than a female Montezuma Oropendola, so it can look like a dark oropendola. Look for the all black plumage and the neck ruff. Females lack the ruff, so lean on the dull black plumage, the smaller size and the setting beside a colony.

Names and lore in Costa Rica

In Costa Rica and Nicaragua the usual Spanish name is Vaquero Grande. Elsewhere you may hear vaquero gigante in Mexico, and vaquero pirata, tordo gigante or chamón gigante in Colombia.

Status and conservation

Listed as a resident (R) on the AOCR list and rated Least Concern by the IUCN because its population is very large.

Photography tips

Watch the tops of trees holding oropendola nests, where the cowbirds wait for a chance at an unguarded nest. Colonies in open roadside trees let you pull over and scan for cowbirds perched nearby.