Montezuma Oropendola is a familiar bird on the Atlantic slope between eastern Mexico and extreme western Panama; it also is found on the Pacific slope in Nicaragua and in northwestern Costa Rica. This large bird often is common at the edge of humid lowland forests, and in adjacent second growth and plantations. Montezuma Oropendola nests colonially, often in isolated large trees; such a setting makes the clusters large, hanging, basket-like nests even more conspicuous. Montezuma Oropendolas are highly dimorphic in size; males may be up twice the weight of females. This species is polygynous, and dominant 'alpha' males perform most copulations at a colony (although subordinate males apparently are able to copulate with some females, presumably away from the colony and the presence of the alpha male). The loud, gurgling song of the male is given as the male bows forward, cocking the tail and spreading the wings. Montezuma Oropendolas usually forage in small groups in the canopy, searching for fruit and large insects; at least occasionally they also eat small vertebrates. Montezuma Oropendola easily is recognized by its large size, chestnut body plumage, yellow outer rectrices, bicolored bill, and the pale patch of bare skin on the sides of the head.