Geese. A goose is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera Anser, Branta, and Chen, the latter being commonly placed within the genus Anser. Some other birds, mostly related to the shelducks, have goose as part of their names. More distantly related members of the family Anatidae are swans, most of which are larger than true geese, and ducks, which are smaller. The term goose is more properly used for a female bird, while gander refers specifically to a male one. Young birds before fledging are called goslings. The collective noun for a group of geese on the ground is a gaggle; when in flight, they are called a skein, a team, or a wedge; when flying close together, they are called a plump. The word goose is a direct descendant of Proto-Indo-European root, ghans-. The three living genera of true geese are: Anser, grey geese, including the greylag goose, and domestic geese; Chen, white geese, such as the snow goose; and Branta, black geese, such as the Canada goose. Two genera of geese are only tentatively placed in the Anserinae; they may belong to the shelducks or form a subfamily on their own: Cereopsis, the Cape Barren goose, and Cnemiornis, the prehistoric New Zealand goose. Either these or, more probably, the goose-like Coscoroba swan is the closest living relative of the true geese. Fossils of true geese are hard to assign to genus; all that can be said is that their fossil record, particularly in North America, is dense and comprehensively documents many different species of true geese that have been around since about 10 million years ago in the Miocene. The aptly named Anser atavus from some 12 million years ago had even more plesiomorphies in common with swans. In addition, some goose-like birds are known from subfossil remains found on the Hawaiian Islands. Geese are monogamous, living in permanent pairs throughout the year; however, unlike most other permanently monogamous animals, they are territorial only during the short nesting season. Paired geese are more dominant and feed more, two factors that result in more young. Some mainly Southern Hemisphere birds are called geese, most of which belong to the shelduck subfamily Tadorninae. These are: Orinoco goose, Neochen jubata. Egyptian goose, Alopochen aegyptiaca. The South American sheldgeese, genus Chloephaga. The prehistoric Malagasy sheldgoose, Centrornis majori. Others: The spur-winged goose, Plectropterus gambensis, is most closely related to the shelducks, but distinct enough to warrant its own subfamily, the Plectropterinae. The blue-winged goose, Cyanochen cyanopterus, and the Cape Barren goose, Cereopsis novaehollandiae, have disputed affinities. They belong to separate ancient lineages that may ally either to the Tadorninae, Anserinae, or closer to the dabbling ducks. The three species of small waterfowl in the genus Nettapus are named pygmy geese.