Brown booby

The brown booby (Sula leucogaster) is a large seabird of the booby family Sulidae, of which it is perhaps the most common and widespread species. It has a pantropical range, which overlaps with that of other booby species. The gregarious brown booby commutes and forages at low height over inshore waters. Flocks plunge-dive to take small fish, especially when these are driven near the surface by their predators. They nest only on the ground, and roost on solid objects rather than the water surface.

The booby's head and upper body (back) is covered in dark brown to blackish plumage, with the remainder (belly) being a contrasting white. The bare-part colours vary geographically, but not seasonally. The species also displays sexual dimorphism of the bare part colours, the males having a blue orbital ring, as opposed to the yellow orbital ring of the female.

Female boobies reach about 80 centimetres (31 in) in length; their wingspans measure up to 150 cm (4.9 ft), and they can weigh up to 1,300 g (2.9 lb). Male boobies reach about 75 centimetres (30 in) in length; their wingspans measure up to 140 cm (4.6 ft), and they can weigh up to 1,000 g (2.2 lb).

Unlike other species of sulid, the juvenile plumage already resembles that of the adult. They are grey-brown with darkening on the head, upper surfaces of the wings and tail, while the lower breast and underpart plumages are heavily flecked brown on white. Juveniles of subspecies S. l. brewsteri are once again distinct in having the underpart plumage more evenly mouse brown.

Their beaks are quite sharp and contain many jagged edges. They have fairly short wings resulting in a fast flap rate, but long, tapered tails. While these birds are typically silent, bird watchers have reported occasional sounds similar to grunting or quacking.