Sula Brisson, Ornith., i, p. 60, vi, p. 494 (1760).
Type by first desig., Sula leucogaster Linn.
In this genus the bill is powerful, straight, compressed and pointed; the culmen is flattened, broad at the base, curved at the end but not hooked - the upper mandible has a groove on each side near the culmen; the nostril is completely closed in adults, minute and basal in young birds ; the inner margins of both mandibles are serrated, more strongly so towards the tip; the wings are long and pointed ; the tail long and wedge-shaped ; the tarsus is short but powerful, with the outer and middle toes equal and the claw of the middle toe broad and pectinated.
The Boobies and Gannets inhabit the tropical and temperate seas but are only very casual visitors to the shores of India, three species having been known to occur, one of which, dactylatra, has been represented by two subspecies, one an Eastern, the other a Western form.
Key to Species.
A. Tail-feathers fourteen.
a. Head, neck and upper parts brown in adults; feet pale yellow…………..S. leucogaster, p. 285,
b. Head, neck, body and tail white in adults; feet red …………..S. sula, p. 286.
B. Tail-feathers sixteen; head, neck and body white in adults: tail blackish; feet slaty…………..S. dactylatra, p. 287.