The dorhawk or nightjar.
nightjar definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
any of a family (Caprimulgidae) of goatsuckers; esp., the common European nightjar (Caprimulgus europaeus)
Origin: night plush jar: from the whirring noise made by the male
nightjar definition by American Heritage Dictionary
A goatsucker, especially Caprimulgus europaeus of Europe, having gray and brown mottled plumage with long, slender white wings and a short bill.
Origin: night + jar2 (from its harsh call).