Proposal (232) to South American Classification Committee
Reassign Chordeiles vielliardi to genus Nyctiprogne
Effect on South American CL: This proposal would reassign a species on our base list, Chordeiles vielliardi, to the genus Nyctiprogne.
Background: Chordeiles vielliardi (Bahian Nighthawk) was described from two specimens, an adult male and a juvenile male, taken near Manga, Bahia, in the São Francisco River valley of northeastern Brazil (Lencioni-Neto 1994). The author diagnosed the bird as a small caprimulgid without white markings on the wing, tail, or throat, and allocated it to the genus Chordeiles. He concluded that it was most closely related to the sympatric C. pusillus (Least Nighthawk) because of its "relatively small bill and lack of prominent rictal bristles proportions near those of C. pusillus and approaching that species in its pattern, habitat and behavior" (translation from description in French). The new species was not tape recorded, and the only vocalization heard, a "bit-bit" delivered during the day when the birds were flushed from day roosts, was described as similar to a vocalization of C. pusillus.
Almost concurrently, Bret Whitney, José Fernando Pacheco, Paulo Sérgio Moreira da Fonseca, Richard Webster, Guy Kirwan, and Juan Mazar Barnett were independently collecting data on a small nightjar in the São Francisco valley near Januária in northern Minas Gerais. They captured, photographed, measured, then released one individual, and tape-recorded others. They described their bird as being similar to Band-tailed Nighthawk, Nyctiprogne leucopyga, except that it lacked the median tail-band and white lateral throat patches that characterize all known populations of that species (Whitney et al. 2003). Whitney and colleagues subsequently examined an unidentified caprimulgid specimen deposited at Rio that had been recovered in April 1994 near Mocambinho, Minas Gerais. This specimen proved to be the Nyctiprogne nighthawk that they had observed at Januária. Comparison of that specimen with the holotype of Chordeiles vielliardi left no doubt that the Minas Gerais birds were referable to that form.
Whitney et al. (2003) provide several types of evidence to support their contention that the nighthawks described as Chordeiles vielliardi should be reassigned to the genus Nyctiprogne. This evidence can be summarized as follows:
1. Morphology: Nyctiprogne leucopyga has a conspicuous white median band on the three outer rectrices, lacks white in the primaries, and has whit on the throat restricted to a small rounded patch on either side. Chordeiles vielliardi is almost identical to N. leucopyga, differing primarily in lacking the median tail-band. Chordeiles pusillus, the purported closest relative of vielliardi, differs dramatically. All three species are illustrated in Handbook of Birds of the World, Volume 5.
2. Vocalizations: Spectrograms of the songs of the three species show clear similarities in pattern and frequency between the songs of Chordeiles vielliardi and N. leucopyga (songs consisting of 3 elements, with first separated from the other two by a long pause), whereas the songs of C. pusillus are completely different in note shape, number of notes, between-note intervals, overall duration, and frequency. Recordings of all three species are presented by Ranft and Cleere (1998).
3. Habitat: C. vielliardi is most common along the Rio São Francisco where the river is bordered by gallery woodland and brushy growth, and is uncommon or absent from disturbed areas where semi-arid caatinga scrub now dominates the river edge. Similarly, N. leucopyga is a bird of várzea and igapó edge and, to a lesser extent, thick brush on dry ground, almost always in the immediate vicinity of water. In contrast, C. pusillus inhabits seasonally dry or arid open country, such as savannas, campinas, and caatinga scrub, often far from water.
4. Behavior: C. vielliardi roosts in loose colonies of up to 30+ birds during the day, roosting in dense, often brushy vegetation. The birds were noted to perch "crossways" (perpendicular to the substrate) from ca. 0.2 to 1.5 m above the ground (never on the ground, contra Lencioni-Neto 1994), sometimes with 2-4 individuals huddled side-by-side on thin, horizontal limbs. When flushed during the day, individuals uttered short single or double notes, apparently the vocalizations described by Lencioni-Neto (1994). Birds sang from day-roost perches, and were never observed to sing in flight, although they did commonly give short calls. Foraging was entirely aerial. Flight characteristics were described as shallow, fluttery wing-beats interspersed with occasional deeper strokes, and much short-distance gliding with the wings held in a dihedral position. Birds did not begin foraging until nearly dusk, and then, typically flew low (1-10 m) over the water. Whitney et al (2003) note that these descriptions of behavior and habitat are almost exactly as they have observed for N. leucopyga, and very different from C. pusillus, which roosts directly on open ground (usually among pebbles and rocks, and away from concealing brush); begins foraging 20-30 minutes before sunset, attaining heights of 10-50+ m above ground shortly after leaving roosts; flies with very different attitude and progression; and sings from both perches and in flight.
Whitney et al (2003) conclude that parallels in voice, plumage, habitat and behavior demonstrate that C. vielliardi is a member of the N. leucopyga complex, and that no particular affinity to C. pusillus or other members of that genus is suggested. They also summarize reasons why vielliardi is more closely allied with Nyctiprogne than with Lurocalis or Caprimulgus. In addition to the generic transfer, they also suggest a different English name, "Plain-tailed Nighthawk" to call attention to the most diagnostic plumage character of vielliardi. Lencioni-Neto (1994) did not propose and English or Portuguese name for vielliardi. Bahian Nighthawk was introduced by Cleere (1998, 1999) and subsequently employed by Ranft & Cleere (1998) and Holyoak (2001). "Caatinga Nighthawk" was coined by Stattersfield et al. (1998).
Analysis & Recommendation: Whitney et al. (2003) do an excellent job of summarizing the close parallels in morphology, voice, habitat and behavior between C. vielliardi and N. leucopyga, and in showing the dissimilarities of both species to C. pusillus. At the same time, differences in morphological and vocal characters (as demonstrated by sonograms) between vielliardi and all known populations of leucopyga are shown to be consistent with species-level differences within the Caprimulgidae.
On a personal note, my own field experience with all three species accords precisely with the observations of Whitney et al. with regard to behavioral similarities between vielliardi and leucopyga (e.g. Perching behavior, flight characteristics, vocal behavior, habitat selection), and with regard to differences between those species and C. pusillus. Similarly, my tape recordings of vielliardi reveal a voice that is recognizably different from that of leucopyga, while still showing a number of similarities. No such similarities exist between my recordings of vielliardi and anything that I have recorded from C. pusillus.
My recommendation is a YES vote on reassigning Chordeiles vielliardi to the genus Nyctiprogne.
The issue of a change in the English name probably requires a separate proposal, which I can also draft if need be. For the record, I would also favor the change recommended by Whitney et al. Since the describer of vielliardi did not suggest an English name, and two different English names (Bahian Nighthawk and Caatinga Nighthawk) have been used in the few short years since the bird's description, one could argue that there is no truly established name. Furthermore, the name Bahian Nighthawk is misleading in the sense that the bird seems to be most common and widespread in Minas Gerais. The name Caatinga Nighthawk is misleading given what is now known of its preferred habitat. Conversely, the suggested name of Plain-tailed Nighthawk highlights the most important plumage feature of the bird, and is a sensible counterpoint to the name given to its presumed closest relative, the Band-tailed Nighthawk, Nyctiprogne leucopyga.
Cleere, N. 1998. Nightjars. Yale University Press, New Haven, Connecticut, and London.
Cleere, N. 1999. Family Caprimulgidae (Nightjars). Pp. 302-386 in: del Hoyo, J., Elliott, A. & Sargatal, J. (Eds.) Handbook of the birds of the world. Vol. 5. Lynx Edicions, Barcelona.
Holyoak, D. T. 2001. Nightjars and their allies. Oxford Univ. Press, Oxford.
Lencioni-Neto, F. 1994. Une nouvelle espèce de Chordeiles (Aves, Caprimulgidae) de Bahia (Brésil). Alauda 62 :242-245.
Ranft, R. and Cleere, N. 1998. A sound guide to nightjars and related birds. Pica Press, Robertsbridge & Yale University Press, New Haven.
Stattersfield, A. J., Crosby, M. J., Long, A. J. & Wege, D. C. 1998. Endemic Bird Areas of the world: priorities for biodiversity conservation. BirdLife International, Cambridge, U. K.
Whitney, B. M., J. F. Pacheco, P. S. M. Fonseca, R. E. Webster, G. M. Kirwan and J. M Barnett. 2003. Reassignment of Chordeiles vielliardi Lencioni-Neto, 1994, to Nyctiprogne Bonaparte, 1857, with comment on the latter genus and some presumably related chordeilines (Caprimulgidae). Bull. B. O. C. 123:103-112.
Kevin Zimmer, August 2006
Comments from Remsen: "YES. One of the most convincing non-genetic data-sets ever for generic reassignment ."
Comments from Robbins: "YES. Whitney et al. (2003) provided conclusive evidence for placing vielliardi in Nyctiprogne."
Comments from Stiles: "YES. Different types of evidence all point to this conclusion. The conservatism of the "camouflaged" plumage in Caprimulgidae has probably led to various distinct evolutionary lineages being lumped, and I would not be overly surprised to see more changes like this one being proposed in the future."
Comments from Stotz: "YES This was clearly misplaced in Chordeiles, and the published arguments are clearly sound."
Comments from Jaramillo: "YES - For the record, and Plain-tailed Nightjar seems quite logical and reasonable."
Comments from Pacheco: "YES. Como coautor da proposta publicada, um voto apenas em reafirmação."