The Collaborative International Dictionary of English v.0.48:

Chuck-Will's-widow \Chuck`-Will's-wid"ow\, n. (Zool.)
   A large whippoorwill-like bird (a species of goatsucker)
   (Caprimulgus carolinensis, formerly Antrostomus
   Carolinensis), of the southern United States; -- so called
   from its note.
   [1913 Webster]