The Herring gull (Larus argenteus) is found throughout the year around coasts and inland rubbish tips, fields, large reservoirs and lakes. Adults have light grey backs, white under parts, and black wing tips with white 'mirrors'. Their legs are pink, with webbed feet and they have heavy, clear yellow eyes, and slightly hooked bills marked with a red spot. Male and female gulls get the red spot when they are fully grown, in about four years. Studies have shown that newly hatched chicks were fed by their parents only after they pecked at the adults' bills. It became clear that the red spot on the adult gull's bill was a crucial visual cue in a chick's demands to be fed, and that the chick's attraction to the red spot on the bill was instinctive. The males are larger than females; the sexes have similar plumage. Although they prefer fresh water when they can get it, herring gulls have adapted to drinking seawater. Special glands above their eyes desalinate the water, then excrete the excess salt in a viscous fluid that can sometimes be seen issuing from the bird’s nostrils and running down its bill.