The Collaborative International Dictionary of English v.0.48:

Hawk-eyed \Hawk"-eyed`\ (-[imac]d`), a.
   Having very keen vision; sharp-sighted; discerning. [WordNet
   sense 1]

   Syn: keen-sighted, lynx-eyed, quick-sighted, sharp-eyed,
        sharp-sighted.
        [1913 Webster]

   2. alert to possible danger. [WordNet sense 2]

   Syn: argus-eyed, open-eyed, unsleeping, vigilant, wary,
        watchful.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

hawk-eyed
    adj 1: having very keen vision; "quick-sighted as a cat" [syn:
           argus-eyed, hawk-eyed, keen-sighted, lynx-eyed,
           quick-sighted, sharp-eyed, sharp-sighted]