Source : Webster's Revised Unabridged Dictionary (1913)

Vesper \Ves"per\, a.
   Of or pertaining to the evening, or to the service of
   vespers; as, a vesper hymn; vesper bells.

   {Vesper sparrow}, the grass finch. See under {Grass}.

Source : WordNet®

vesper sparrow
     n : common North American finch noted for its evening song [syn:
          {grass finch}, {Pooecetes gramineus}]