Royal tern Sterna maxima

• Sexes similar
• Dives into water for prey
• Large tern with fairly thick orange bill
• Fairly long, deeply forked tail
• Spiky crest at the rear of the head
• Pale underwing with dark tips to outer primaries
• Takes three years to reach full adult plumage

Adult alternate:

• Black legs
• Black cap
• White face, neck, breast, and belly
• Pale gray back and upperwings
• White rump and tail, often with dark edgings
• Plumage held in Spring (March to May)

Adult basic:

• White forehead and crown
• Black mask extends rearward from eye to spiky crest at rear of head
• White eye ring in dark mask
• Outer primaries and tail feathers darken with wear, becoming dark gray in basic plumage

Juvenile:

• Pale legs
• White forehead and crown
• Dark brown mask extending rearward from eye to spiky crest at rear of head
• White neck, breast, and belly
• Pale gray back
• Dark brown carpal bar
• Dark brown uppersurface to secondaries and outer primaries
• Gray tail with dark margins

Immature:

• First-year birds generally have dark secondaries and outer primaries, and a slightly more extensive black mask
• Second-year birds are generally very similar to adults in alternate plumage but often have darker primaries and secondaries and white tips to feathers in black cap

Similar species:

When identifying terns, it is safest to use a combination of field marks instead of relying on a single characteristic. Elegant Terns are slightly smaller and slenderer, with more slender, drooping bills and, when not in alternate plumage, lack a pale eyering in the dark mask. The Caspian can be separated from the Royal by its thicker, reddish bill, dark wedge on the outer portion of the underwing, its more shallowly-forked tail and its tendency to have an almost complete cap in basic and immature plumages. The smaller Sterna terns have slimmer, black or black-tipped bills, slimmer bodies and wings and a much more deeply-forked tail.