Whooper swans (cygnus cygnus) herd on water, martin mere, uk

uk horizontals swan vertebrates water migrate waterbird birds martin animals wetland hunters sociable horizontal monogamous wildlife carnivorous nature predator flock lakes waterbirds wetlands migrates aves predation crowd zoology aquatic social flocks whooper crowds bird vertebrate migratory carnivore swans predators meat mere ponds cygnus group swans migrating water flocking anatidae groups herd monogamy lake anseriformes hunter fauna cygnus pond animal