With their raucous shrieks, gurgles and flashing yellow tails, they are easy to spot. This fruit-eating bird is a member of the blackbird family, which includes orioles, starlings, caciques, meadowlarks, cowbirds and grackles. The male Montezuma oropendola is about 19 inches long, similar to a large cowbird. Females are smaller in length and weight.
Males court the females with unusual displays of bows, wing flapping and strange gurgle-like calls.
Oropendolas nest in colonies ranging in size from four to over one hundred nests, but more typically between thirty and forty. The large baglike nests, well over three feet in length, are most often found at the edge or in a clearing of the rainforest. The females weave them and usually lay two eggs at a time, but the mortality rate is high in oropendola colonies due to predation by toucans, snakes, monkeys and botfly larvae. Oropendola young also have a higher rate of survival if the Giant Cowbird lays its eggs in the oropendola nest. The cowbird young hatches earlier than the oropendola and eats the eggs and larvae of the botflies, enabling the young oropendola to survive until fledging.