The eastern whip-poor-will (Antrostomus vociferus, also called 'whip-o-will', 'whip o' will', etc.) is a medium-sized (22–27 cm; 8.7-10.6 ins.) bird within the nightjar family, Caprimulgidae, from North America. The whip-poor-will is commonly heard within its range, but less often seen because of its camouflage. It is named onomatopoeically after its song. This medium-sized nightjar measures 22–27 cm (8+1⁄2–10+1⁄2 in) in length, spans 45–50 cm (17+1⁄2–19+1⁄2 in) across the wings and weighs 42–69 g (1+1⁄2–2+7⁄16 oz). Further standard measurements are a wing chord of 14.7 to 16.9 cm (5+13⁄16 to 6+5⁄8 in), a tail of 10.5 to 12.8 cm (4+1⁄8 to 5+1⁄16 in), a bill of 1 to 1.4 cm (3⁄8 to 9⁄16 in) and a tarsus of 1.5 to 1.8 cm (9⁄16 to 11⁄16 in). Adults have mottled plumage: the upperparts are grey, black and brown; the lower parts are grey and black. They have a very short bill and a black throat. Males have a white patch below the throat and white tips on the outer tail feathers; in the female, these parts are light brown. (Source: Wikipedia.org, CC BY-SA)