Source : Webster's Revised Unabridged Dictionary (1913)

Kestrel \Kes"trel\ (k[e^]s"tr[e^]l), n. [See {Castrel}.]
   (Zo["o]l.)
   A small, slender European hawk ({Falco alaudarius}), allied
   to the sparrow hawk. Its color is reddish fawn, streaked and
   spotted with white and black. Also called {windhover} and
   {stannel}. The name is also applied to other allied species.

   Note: This word is often used in contempt, as of a mean kind
         of hawk. ``Kites and kestrels have a resemblance with
         hawks.'' --Bacon.