Family LARIDAE Rafinesque, 1815
Introduction
Laridae, the gulls and terns, are a large polyphyletic family with 97 species in 15 genera. They are cosmopolitan, although numbers decline in the tropics. Australian family members number 26 species, referred to seven genera. These 26 species are represented by 33 ultrataxa. In all species the sexes are alike.
All larids are nomadic or exceptional migrants. They show a marked difference between breeding and non-breeding plumages. All feed on marine vertebrates and invertebrates. Their tongues have elongate papillae that assist in retention of prey. In all species the leading three toes are webbed and the hind toe is small and weak. Pair bonds are monogamous. Gull nests are untidy, built on the ground or other level surfaces, and constructed of vegetation. Terns, noddies and ternlets also construct rudimentary nests either on the ground or, as in the case of some noddies and the ternlets, on tree limbs. An exception is the genus Gygis, members of which do not construct a nest; instead a single elliptical egg is secured in a slight notch on a tree limb. Clutches vary from a single oval egg to four eggs. Base colours vary from greyish or creamy white to ochre-olive. Each egg is splotched or spotted by darker tones. Like all members of the order the young are precocial, nidifugous and ptilopaedic.
Two distinctive groups are recognised in Australia: the gulls and the terns. Australian gulls are large to medium sized. They have white plumage, and backs and wings shaded black in the larger species to silver-grey in the one medium-sized species. The tails are either rounded or squared; their legs and bills vary according to season from red or red-yellow. Gull bills are hooked at their extremity, have a tapered nail, and a marked gonydeal angle. All gulls are found in marine and freshwater habitats and often on land where they scavenge for food; they are omnivorous.
The second group are the medium- to small-sized terns. These have white plumage, with greyish backs and wings, one (the Roseate Tern, Sterna dougalli) has a delicate flush of rosy plumage on the underparts. Their legs and beaks are of varied in colour; the tails are squared or forked. Terns feed by plunge-diving or dipping on water surface; they seldom feed on or over land. Terns frequent both fresh and saltwater habitats. Tropical noddies and ternlets are either sooty brown, with or without a white cap, pure white to pale grey, or pure white.
A summary of the family is given by Christidis & Boles (2008: 143).
General References
Christidis, L. & Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. Melbourne : CSIRO Publishing 288 pp.