Gular skin (throat skin), in ornithology, is an area of featherless skin on birds that joins the lower mandible of the beak (or bill) to the bird's neck. Other vertebrate taxa may have a comparable anatomical structure that is referred to as either a gular sac, throat sac, vocal sac or gular fold.
In birds
Gular skin can be very prominent, for example in members of the order Suliformes (gannets, frigatebirds, and cormorants) as well as in pelicans (which likely share a common ancestor). In many species, the gular skin forms a flap, or gular pouch, which is generally used to store fish and other prey while hunting.
In cormorants, the gular skin is often brightly coloured, contrasting with the otherwise plain black or black-and-white appearance of the bird. This serves a function in social signalling, since it becomes more pronounced in breeding adults.