megalestris skua

from The Collaborative International Dictionary of English v.0.48

Skua \Sku"a\, n. [Icel. sk?fr, sk?mr.] (Zool.)
   Any jager gull; especially, the {Megalestris skua}; -- called
   also {boatswain}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Jager \Ja"ger\, n. [G. j[aum]ger a hunter, a sportsman. Cf.
   {Yager}.] [Written also {jaeger}.]
   1. (Mil.) A sharpshooter. See {Yager}.
      [1913 Webster]

   2. (Zool.) Any species of gull of the genus {Stercorarius}.
      Three species occur on the Atlantic coast. The jagers
      pursue other species of gulls and force them to disgorge
      their prey. The two middle tail feathers are usually
      decidedly longer than the rest. Called also {boatswain},
      and {marline-spike bird}. The name is also applied to the
      skua, or Arctic gull ({Megalestris skua}).
      [1913 Webster]