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.
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).
WordNet (r) 3.0 (2006):
n 1: rapacious seabird that pursues weaker birds to make them
drop their prey