common tern (sterna hirundo) is sitting on the nest

bird birds breeding chick chicken closeup colony common 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 ovicell ovum place replication reproduction rookery sea seabird seagull semiaquatic shell site sitting spring sterna tern