Voice and Taxonomy of Caprimulgus (rufus) otiosus (Caprimulgidae), with a Reevaluation of Caprimulgus rufus Subspecies

Abstract

The St. Lucia Nightjar (Caprimulgus otiosus) exhibits minimal vocal and plumage differentiation from mainland forms of the Rufous Nightjar (C. rufus), and, therefore, we consider otiosus conspecific with rufus. Caprimulgus rufus otiosus appears to be resident on the northeastern section of St. Lucia, Lesser Antilles; specimen records from Venezuela are considered erroneous. We recognize the following described subspecies: otiosus (St. Lucia), minimus (Costa Rica to N. Venezuela), rufus (NW Brazil, S. Venezuela, east through the Guianas, and south to south of the Rio Amazonas), and rutilus (S. Brazil, N. Argentina, E. Bolivia). Resumen. Las vocalizaciones y el plumaje del tapacaminos de Santa Lucia {Caprimulgus otiosus) y de la forma continental C. rufus, son muy parecidas, por lo que se les considera como conespecificos. Caprimulgus rufus otiosus aparentemente es residente de la seccion noreste de Santa Lucia en las Antillas Menores; consideramos que los registros de Venezuela son erroneos. Nosotros reconocemos las siguientes subespecies descritas: otiosus (Santa Lucia), minimus (de Costa Rica al N de Venezuela), rufus (NW Brazil, S Venezuela, E de las Guyanas hasta el lado sur del Rio Amazonas), y rutilus (S Brazil, N Argentina y E Bolivia). In the latest A.O.U. Check-list (1983), the Lesser Antillean form (otiosus) of the wide-ranging Rufous Nightjar (Caprimulgus rufus) was elevated to species status. Previously, the St. Lucia Nightjar (C. otiosus) had been regarded as an isolated subspecies of C. rufus by most authors (Bangs 1911; Cory 1918; Griscom and Greenway 1937; Peters 1940; Bond 1947, 1959, 1977), although Wetmore and Phelps (1953) believed that otiosus deserved specific recognition. The A.O.U. (1983) gave the following rationale for treatment of otiosus as a species, ". . . it seems best to retain C. otiosus as specifically distinct until its status is determined." Herein we demonstrate that otiosus shows minimal vocal and plumage differentiation from mainland forms of C. rufus, and is best treated as a subspecies of C. rufus. METHODS AND MATERIALS Study skins were accumulated at the Academy of Natural Sciences, Philadelphia (ANSP) for plumage color and pattern comparisons. Wing chord and length of central rectrices were taken using dial calipers to the nearest 0.1 mm. All tape recordings of otiosus were made on the windward side of St. Lucia, West Indies on 7 May 1988 and 29 April 1989. Tape recordings were made using a Sony TCM 5000 cassette recorder, with a Sennheiser ME 80 shotgun microphone. Additional recordings were obtained from Hardy et al. (1988). Sonagrams were produced with "SoundEdit" of Farallon Computing, Inc., Emeryville, California, and "Canary" of the Bioacoustics Research Program at the Cornell Laboratory of Ornithology, Ithaca, New York.