The Collaborative International Dictionary of English v.0.48:

Vesper \Ves"per\, a.
   Of or pertaining to the evening, or to the service of
   vespers; as, a vesper hymn; vesper bells.
   [1913 Webster]

   Vesper sparrow, the grass finch. See under Grass.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vesper sparrow
    n 1: common North American finch noted for its evening song
         [syn: vesper sparrow, grass finch, Pooecetes
         gramineus]