Caspian tern Sterna caspia


Identification Tips:

Adult alternate:

Adult basic:

Juvenile:

Immature:

Similar species:

When trying to identify terns, it is safest to use a combination of field marks instead of relying on a single field mark. The Royal and Elegant terns are the only other large, orange-billed terns and are quite similar. Elegant Terns are very small compared to Caspians, are very slim-winged, have slimmer orange bills, have much more forked tails and less black on the undersurface of the primaries. The Caspian can be separated from the Royal by its thicker, reddish bill, dark wedge on the outer portion of the underwing, more shallowly-forked tail, broader wings 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.

Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.


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