Bird wing

Bird wings are a paired forelimb in birds. The wings give the birds the ability to fly, creating lift.

Terrestrial flightless birds have reduced wings or none at all (for example, moa). In aquatic flightless birds (penguins), wings can serve as flippers.^[1]

^ Vargas, A. O.; Fallon, J. F. (2005). "The Digits of the Wing of Birds Are 1, 2, and 3. A Review". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 304 (3) (Journal of Experimental Zoology Part B: Molecular and Developmental Evolution ed.): 206–219. doi:10.1002/jez.b.21051. PMID 15880771.