Birds of America
By John James Audubon, F. R. SS. L. & E.
GENUS II.--STERNA, Linn. TERN.
Bill longer than the head, rather stout or slender, nearly straight,
compressed, very acute; upper mandible with the dorsal line slightly arched, the
ridge rather broad and convex at the base, gradually narrowed toward the end,
sides convex, edges sharp and direct, tip acute; nasal groove short; lower
mandible with the angle very narrow, acute, extending to the middle, the dorsal
line straight, the sides slightly convex, nearly erect, the sharp edges
inflected, the tips very acute. Nostrils basal, lateral, linear, direct. Head
rather large, oblong; neck of moderate length and thick; body slender. Feet
short, moderately stout; tibia bare for a considerable space; tarsus short,
roundish, covered all round with small scales; first toe very small, third
longest, fourth a little shorter; anterior toes connected by emarginate webs.
Claws slightly curved, compressed, acute. Plumage soft, close, blended, rather
compact on the back and wings. Wings extremely long, narrow, and pointed, the
first quill longest, the rest rapidly graduated. Tail long, generally forked,
of twelve feathers. Tongue very slender, tapering, with the point slit;
oesophagus extremely wide; proventricular belt complete; stomach rather small,
moderately muscular, with the epithelium dense and longitudinally rugous;
intestine of moderate length, rather narrow; coeca small.