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 bird crowds vertebrate carnivore migratory swans predators meat mere ponds cygnus group swans migrating water flocking anatidae groups herd anseriformes lake monogamy hunter fauna cygnus pond animal