pared to the similar terns, with fully webbed feet. The bill is generally heavy and slightly hooked, with the larger species having stouter bills than the smaller species. The bill colour is often yellow with a red spot for the larger white-headed species and red, dark red or black in the smaller species. Gulls are generalist species that can thrive in various environments and survive on a widely varied diet. They are the least specialised of all the seabirds, and their morphology allows for equal adeptness in swimming, flying, and walking. They are more adept walking on land than most other seabirds, and the smaller gulls tend to be more manoeuvrable while walking. The walking gait of gulls includes a slight side to side motion, something that can be exaggerated in breeding displays. In the air, they are able to hover and they are also able to take off quickly with little space. The general pattern of plumage in adult gulls is a white body with a darker mantle; the extent to which the mantle is darker varies from pale grey to black. A few species vary in this, the ivory gull is entirely white, and some like the lava gull and Heermann's gull have partly or entirely grey bodies. The wingtips of most species are black, which improves their resistance to wear and tear, usually with a diagnostic pattern of white markings on or near the primary feather tips. The head of a gull may be covered by a dark hood or be entirely white. The plumage of the head varies between breeding and non-breeding seasons. In dark-hooded gulls, the hood is lost out of the breeding season, usually leaving a diffuse dark spot or mask through or behind the eye; in white-headed gulls, nonbreeding heads often have dark streaking on the head and ne