Plain-tailed Nightjar as originally described in the genus Chordeiles was generically misplaced.  In the booklet that comes with the CD A Sound Guide to Nightjars and Related Nightbirds, Ranft and Cleere state: "Chordeiles veilliardi (Lencioni-Neto 1995) was erroneously described in that genus.

It is clearly a member of the genus Nyctiprogne, as documented by Bret M. Whitney [and others]."

Indeed such a paper has now been published: see the second reference.

Plain-tailed Nighthawk     Nyctiprogne vielliardi
ec Brazil: Bahia & Minas Gerais, along Rio São Francisco
insert after: Nyctiprogne leucopyga
Frederico Lencioni-Neto,
Une nouvelle espèce de Chordeiles (Aves, Caprimulgidae) de Bahia (Brésil)
Alauda 62, 4 (1994): 241-245


Bret M. Whitney , José Fernando Pacheco, Paulo Sérgio Moreira da Fonseca, Richard E. Webster, Guy M. Kirwan & Juan Mazar Barnett
Reassignment of Chordeiles veilliardi Lencioni-Neto, 1994, to Nyctiprogne Bonaparte, 1857, with comments on the latter genus and some presumably related chordeilines (Caprimulgidae)
Bulletin B.O.C. 123 (2): 103–112

To my knowledge, no other specimens have since been observed, let alone photographed or collected. The specific scientific name (solala) of Nechisar Nightjar means "single-winged" . . .

Doubts have been cast on the validity of this taxon, as can be expected when a species is described from not even half a bird.  Forero & Tella (Sexual dimorphism, plumage variability and species determination in nightjars: the need for further examination of the Nechisar Nightjar Caprimulgus solala, Ibis 1997: 407-409) provide illustrations of high variability of characters within a single species (C. ruficollis), and point out that extreme care should be taken.

Nechisar Nightjar     Caprimulgus solala
Ethiopia: Nechisar Plains, Gamo Gofa province
insert after: Caprimulgus natalensis
R.J. Safford, J.S. Ash, J.W. Duckworth, M.G. Telfer & C. Zewdie,
A new species of nightjar from Ethiopia
Ibis 137, 3 (1995): 301-307