Gull the exceptions being Sabine's gull and swallow-tailed gulls, which have forked tails, and Ross's gull, which has a wedge-shaped tail. Gulls have moderately long legs, especially when compared 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. The gulls are generalist feeders. Indeed, they are the least specialised of all the seabirds, and their morphology allows for
Percival Gull 6-cylinder engine was an option. The D.2 variants are known generically as the "Gull Four" (not "Gull IV"). That was despite the Javelin 6-cylinder engine in the Gull Four Mk IIA, and that before the war the Gipsy Major-powered variant was known as the "Gull Major". In 1934, one Gull was modified with cabin doors, revised and shorter glazing, and a faired, single-strut main undercarriage. This version was known as the Gull Four Mk III, (retrospectively P.1D), and those refinements were incorporated in all later Gulls. The final variant was the D.3 "Gull Six", similar to the D.2 "Gull Four