During a recent examination of tern specimens at the University of Colorado Museum, Boulder, Bruce Webb and Peter Moulton found that CU specimen 8108, labelled Common Tern (Sterna hirundo), was an immature Arctic Tern (S. paradisaea). It was one of two terns collected from a flock of “a dozen or more” feeding at a small lake near Windsor, Weld County, Colorado, on 16 September 1912 by Osterhout (1913).