(noun) A rookery is a communal nesting ground for gregarious birds consisting of anywhere from just a few nests to hundreds of nesting pairs in a relatively small area.
About Rookeries, named for the communally-nesting rook (Corvus frugilegus) of Europe and Asia, rookeries are large, clustered nesting colonies. In the rookery, each nest is typically independent, with parent birds caring for only their nestlings and generally disregarding the behavior of other nearby nests.
In some cases, parent birds may be aggressive toward other adults or young birds that invade the personal space of their nest, though that personal space varies widely for different bird species.
Though individual nests are independent, there are benefits for birds to nest in colonial groups. With more adult birds in the area, predators may be spotted more quickly and pose less of a threat to the group as a whole. Multiple adult birds may also gang up on intruders to defend the nesting area if necessary.
Most rookeries are found in wetland areas or locations where many suitable nesting sites may be scarce. Large trees or groups of trees are favored rookery locations, and islands are especially popular for nesting wading birds because the surrounding water provides a natural protective barrier for the nests. Birds can also become accustomed to artificial rookeries, which are usually large towers with multiple nesting platforms to accommodate many bird families.
In general, while the term rookery can be used for any group of colonially nesting birds, it is reserved for nesting areas that occur in trees or on elevated artificial platforms resembling tree-like structures.