pair of birds. one sits on a nest, a partner nearby as a guard territory in the colony

behavior bird birds breeding chick closeup colony common couple duplication egg eggs family fowl fruit gull habitat hatching hen hirundo incubating incubation laying locule loculus mading make nest nesting nestle nestling nidificate nidify nidus on ovum pair place replication reproduction rookery sea seabird seagull semiaquatic shell site sitting spring sterna tern territorial