A gosling is the young of what sort of bird?

A goose is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera Anser (the grey geese and white geese) and Branta (the black geese). Some other birds, mostly related to the shelducks, have "goose" as part of their names. 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.

Source: Wikipedia