\Scaup\ (sk[add]p), n. [See {Scalp} a bed of oysters or
mussels.]
1. A bed or stratum of shellfish; scalp. [Scot.]
2. (Zo["o]l.) A scaup duck. See below.
{Scaup duck} (Zo["o]l.), any one of several species of
   northern ducks of the genus {Aythya}, or {Fuligula}. The
   adult males are, in large part, black. The three North
   American species are: the greater scaup duck ({Aythya
   marila}, var. nearctica), called also {broadbill},
   {bluebill}, {blackhead}, {flock duck}, {flocking fowl},
   and {raft duck}; the lesser scaup duck ({A. affinis}),
   called also {little bluebill}, {river broadbill}, and
   {shuffler}; the tufted, or ring-necked, scaup duck ({A.
   collaris}), called also {black jack}, {ringneck},
   {ringbill}, {ringbill shuffler}, etc. See Illust.. of
   {Ring-necked duck}, under {Ring-necked}. The common
   European scaup, or mussel, duck ({A. marila}), closely
   resembles the American variety.