How to identify the Royal Tern

To correctly identify the Royal Tern (Thalasseus maximus), check each of these features. Birds can be tricky: habit, habitat, and call often confirm a sighting that a single photo cannot.

Size at a glance

Length

45-50 cm (18-20 in)

Wingspan

100-130 cm (39-51 in)

Weight

350-450 g (12-16 oz)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adults have white underparts, pale gray upperparts (mantle and wings), and a black cap. The primaries are darker, appearing silvery-gray from below. The tail is moderately forked and white.

2. 2

   Beak shape

   Shape and color of the bill: a key field mark.

   Long, stout, and sharply pointed. Distinctive bright orange-red color.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Dark brown

4. 4

   Leg color

   Leg and foot color.

   Black

5. 5

   Distinguishing features

   Standout features that separate this species.

   Large size, prominent orange-red bill, and shaggy black crest (especially in breeding plumage).

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles have a mottled gray and white back and wings, often with dark barring. The black cap is less defined, often streaky, and the bill is duller orange-yellow, sometimes with a dusky tip. The tail is less deeply forked and may have a dark subterminal band.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   In breeding plumage, adults have a full, shaggy black cap extending from the forehead to the nape. In non-breeding plumage, the black cap recedes to the nape, becoming streaky or patchy, with a white forehead and crown.

8. 8

   Sexual dimorphism

   How males and females differ.

   Males and females are outwardly similar in plumage and size, though males may be slightly larger on average.

Key field marks

• Bill Color and Shape. Look for the prominent, stout, bright orange-red bill. This is the most distinctive field mark.
• Size and Proportions. It's a large tern, larger than most other terns except the Caspian Tern. Note its relatively long wings and moderately forked tail.
• Plumage (Adult Breeding). Observe the full, shaggy black crest extending from the forehead to the nape, contrasting with white underparts and pale gray upperparts.
• Plumage (Adult Non-breeding). Note the white forehead and crown, with the black cap reduced to a streaky patch on the nape.
• Flight and Foraging. Watch for its characteristic plunge-diving behavior from a moderate height into the water.
• Vocalizations. Listen for its loud, harsh, grating 'kree-e-ek' call.

Explore the Royal Tern