The Collaborative International Dictionary of English v.0.48:

Attagas \At"ta*gas\, Attagen \At"ta*gen\, n. [L. attagen a kind
   of bird, Gr. ?, ?.] (Zool.)
   A species of sand grouse (Syrrghaptes Pallasii) found in
   Asia and rarely in southern Europe.
   [1913 Webster]