Mew gulls have an average length of 40 cm (1.3 ft.), with slender, yellowish-green legs and webbed feet. Male and Female gulls have a similar appearance, although males usually are a bit larger. They have gray wings and back with a plain white head and a greenish-yellow bill. The wingspan is usually around 119 to 122 cm (47 to 48 in.). Young gulls plummage is brown and spotted with tan; their beak is dark with a pink undertone. They will not develop adult coloration until about 27 months. (Felix, 1998; Del Hoya, 1996)
Range mass: 290 to 552 g.
Average mass: 432 g.
Range length: 40 to 46 cm.
Range wingspan: 119 to 122 cm.
Average basal metabolic rate: 2.257 W.