Rookery

A rookery is a breeding colony where animals gather in large numbers to mate, nest, and rear young. The term is most often used for birds, but it can also describe colonies of seals and sea lions. In birds, rookeries may host thousands of individuals; species commonly forming rookeries include gulls, terns, cormorants, pelicans, and penguins. Rookeries are typically located on coastal cliffs, rocky outcrops, islands, beaches, or ice shelves, chosen for access to food resources and relatively low predation risk.

Ecology and behavior at rookeries are influenced by the advantages and costs of crowding. Concentrated nesting allows social information exchange, easier mate selection, and collective defense against some predators, but it also increases the risk of disease transmission, parasitism, and competition for limited nesting sites. Nest structures and defensive behaviors vary by species; some birds nest in dense colonies with minimal territory, while others maintain individual territories within a larger colony. Human disturbance can cause reduced breeding success or relocation of colonies.

Conservation and management considerations commonly focus on protecting rookeries from disturbance, habitat loss, and predation by introduced species. Many rookeries are designated as protected areas or wildlife reserves. Climate change and changes in food availability can affect breeding timing, chick survival, and colony stability, making monitoring and habitat protection important for long-term viability.

The word rookery derives from the rook, a crow-like bird historically known to nest in such sites in Britain; the term broadened to describe other colonial breeders. See also breeding colony and colonial nesting.