Smallest of North American terns. In breeding plumage, note black cap, white forehead and yellow bill with black tip. Remainder of upperparts gray, underparts white, outer 2 primaries black. Sexes similar. Non-breeding plumage similar for all ages: white underparts, gray mantle, dark lesser-coverts, marginal or lesser wing-coverts forming a cubital bar, dark nape and crown with variable white flecking in crown, and dark eye-stripe with white flecking at lores.

Common locally around nesting colonies; uncommon to rare elsewhere. Nests on sand dunes and sandbars close to water among scattered debris and grass.

Year-round resident of coastal southern California. Breeds widely along coastal beaches and major interior rivers of North America. Winters broadly across marine coastlines of Central and South America.