rookery is a colony of penguins (or seals). Male emperor penguins huddle together in a rookery incubating their eggs on their feet. In so doing they reduce the heat loss from their bodies by up to 50%.
it is usually used to describe a location with a group of pinnipeds on shore for the purposes of reproduction. A typical seal rookery would have adult males and females, juveniles and pups. The term rookery has neither quantitative nor legal definition relative to pinnipeds. It is also used to describe any breeding ground for birds and mammals.