Geographic Variation in the Juvenal Plumage of the Lesser Nighthawk (Chordeiles acutipennis)

In attempting to identify a series of Lesser Nighthawks (Chordeiles acutipennis) collected on the Pacific lowlands of Guatemala, and to ascertain the applicable trinomial to use, I encountered a striking degree of variation among juveniles in the collection of the American Museum of Natural History (AMNH). To evaluate the taxonomic usefulness of the juvenal plumage in the species, additional juveniles were borrowed from the University of Michigan Museum of Zoology (UMMZ), the U.S. National Museum of Natural History (USNM), the Carnegie Museum of Natural History (CM), the Field Museum of Natural History (FMNH), and the Moore Laboratory of Zoology (MLZ). A total of 32 juveniles was available for study. Seven plumage groupings arranged north to south can be recognized among these juveniles

ROBERT W. DICKERMAN, The Auk, 98: 619-621