Adult Herring Gulls are similar to California Gulls but are larger, have pinkish legs, a yellow iris, paler backs, and a slightly thicker yellow bill with a more pronounced gonys. First-winter Herring Gulls are extremely similar but usually have entirely black bills and only show contrasting secondaries in flight, and lack contrasting greater secondary coverts. Immature birds are probably best separated by the subtleties of size, shape and bill shape. Some subadult Herring Gulls can have both a red spot and black ring on the bill, as well as yellowish or gray legs, so identify such birds with caution. Adults are darker-backed than Ring-billeds, with a brown eye, heavier head streaking, and a different bill pattern. Immatures are browner overall than immature Ring-billed Gulls and show less contrast between the upperwing coverts and the secondaries. The Lesser Black-backed Gull, increasingly common in the New World, is similar but is longer-winged. Adults are darker-backed, have yellow legs and a pale iris, and first-year birds are darker backed and have dark bills through their first summer at which point their darker back color begins to show. The upperwings of first winter birds also show almost no contrast in flight and at rest. Adult Mew Gulls are smaller with unmarked yellow bills.