It roosts singly or colonially and may form harems. The Cocoi heron nests colonially in trees. This species breeds colonially in marshes, usually nesting in bushes or low trees. They nest colonially in trees, often along with other waterbirds. These bee-eaters are gregarious, nesting colonially in sandy banks. It also nests colonially in crevices on cliff faces. They are gregarious birds which often breed colonially. Many weaver species are gregarious and breed colonially. The guano of gulls and other colonially nesting water-associated birds is rarely connected to histoplasmosis. It displaces native plants, growing colonially in thick monotypic stands. They are gregarious birds, travelling in flocks, hunting cooperatively, and breeding colonially. Most members of this almost worldwide group breed colonially in trees, building large stick nests. The birds breed colonially in spring in "heronries", usually building their nests high in trees. Birds that nest colonially may benefit from increased protection against predation. It nests colonially, with up to 25 nests in one tree.