Source : Webster's Revised Unabridged Dictionary (1913)

Fork-tailed \Fork"-tailed`\, a. (Zo["o]l.)
   Having the outer tail feathers longer than the median ones;
   swallow-tailed; -- said of many birds.

   {Fork-tailed flycatcher} (Zo["o]l.), a tropical American
      flycatcher ({Milvulus tyrannus}).

   {Fork-tailed gull} (Zo["o]l.), a gull of the genus {Xema}, of
      two species, esp. {X. Sabinii} of the Arctic Ocean.

   {Fork-tailed kite} (Zo["o]l.), a graceful American kite
      ({Elanoides forficatus}); -- called also {swallow-tailed
      kite}.