Proposal (256) to South American Classification Committee
Move Caprimulgus candicans from Caprimulgus to Eleothreptus
Effect on SACC: Move White-winged Nightjar Caprimulgus candicans from Caprimulgus to Eleothreptus.
The genus Eleothreptus G. R. Gray, 1840
Morphological characteristics that separate this genus from Caprimulgus are a broader bill, proportionally longer rictal bristles, a short, square tail and partially feathered tarsi. Males also have strongly curved primaries, but the short secondaries of male Sickle-winged Nightjars may have evolved through territorial and courtship display activity and possibly do not constitute a generic character.
Sickle-winged Nightjar Eleothreptus anomalus (Gould, 1838)
Description: A small, sexually dimorphic nightjar, approximately 18 - 20 cm in length and relatively short tailed. Males are generally greyish-brown, often tinged cinnamon, and occasionally show an indistinct buffish collar on the hindneck. They have a pale buffish-white stripe above the eye and an indistinct, greyish-white submoustachial stripe, but lack a white patch on the throat. The primary coverts are cinnamon, which show as a diagnostic pale patch on the closed wing, and the scapulars have distinctive blackish markings, shaped like inverted Christmas trees. The primaries are strongly curved, largely blackish, and the outer six are boldly tipped whitish. The secondaries are extremely short and together with the curved primaries, they form the unique wing shape. The tail is broadly barred cinnamon-buff and the outer three feathers are narrowly tipped whitish or buffish-white. Females are browner, often with longer wings and tails, and lack the distinctive wing shape. The primaries and secondaries are brown, barred tawny and very narrowly tipped buffish-white. Immatures are similar to the adults, although males lack the characteristic wing shape of adult males; juveniles are similar to the adult females (Cleere 1998, 1999).
Range: Central and eastern Brazil, eastern Paraguay and north-eastern Argentina. Probably resident throughout most of its range, although may be a migrant only (September to March?) in the south. Occurs in open country from Distrito Federal and Minas Gerais in Brazil, south and south-west through southern Brazil and eastern Paraguay to Córdoba and Buenos Aires in north-eastern Argentina.
Habitat: Inhabits seasonally flooded grasslands (Miatello et al. 1991, Straneck & Viñas 1994), savanna and grassland with marshes, streams and areas of surface water (Cleere 1998), grassland close to dry degraded woodland and water (Kirwan et al. 1999) and gallery forest, chaco-type woodland and transitional woodland, often near water or marshland (Collar et al. 1992, Pearman & Abadie 1995).
Vocalizations and behaviour: Crepuscular and nocturnal. Calls include rapid chip, tchup or tchut notes, which may be rather weak. Females also utter harsh gzee, gzee sounds (Straneck & Viñas 1994, Cleere 1998). In the breeding season, males perform short display flights during which they make muffled wing flapping sounds (Straneck & Viñas 1994). Roosts and nests on small patches of bare earth amongst clumps of vegetation. Often sits on roads, tracks and low perches at night. When foraging, the fluttery flight is interspersed with glides and sudden changes of direction. Also hunts from the ground by making short sallies (Straneck & Viñas 1994, Pearman & Abadie 1995, Cleere 1998).
Eggs: Very few eggs of this species appear to have been found, collected, or described in the literature. Two were taken on 17 November in São Paulo, Brazil (Ihering 1902); two on 28 November 1925 in Rio Grande do Sul, Brazil (Lowen 1999) and one in mid-November in Santiago del Estero, Argentina (Pereyra 1950). There is also an egg deposited in the Western Foundation for Vertebrate Zoology (catalogue no. 154.874), collected on 7 October 1936 in Minas Gerais, Brazil. The eggs are elliptical, 23.2 - 31. 4 x 18.2 - 22.8 mm, have a buffish or pinkish-buff ground colour, and are finely spotted and scrawled brown and grey.
White-winged Nightjar Caprimulgus candicans (Pelzeln, 1866)
Description: A small, sexually dimorphic nightjar, approximately 19 - 21 cm in length. Males are generally greyish-brown, often tinged cinnamon, and have no collar on the hindneck. They have a whitish stripe above the eye and a whitish submoustachial stripe, but lack a white patch on the throat. Some outer lesser coverts, the alula and the primary coverts are mostly white, although this is not generally visible on the closed wing. The scapulars have strong blackish markings, which are occasionally shaped like inverted Christmas trees. The primaries are curved and are largely white proximally, blackish distally, the amount of white increasing on each feather towards the body. The secondaries are also mostly white, as is the tail, with only the central pair of tail feathers being pale greyish-brown. Females are browner, completely lack white in the plumage, and the primaries and secondaries are brown, regularly barred pale tawny. Immatures and juveniles are similar to adult females (Cleere 1998, 1999).
Range: Central and south-western Brazil, eastern Paraguay and northern Bolivia. Probably resident throughout it's range. Occurs in open, lowland country in Goiás, Brazil and Canindeyú, Paraguay. There are historical records from Mato Grosso and São Paulo, Brazil. The modern record from Beni, Bolivia (Davis & Flores 1994) remains an isolated one to-date.
Habitat: Inhabits open grasslands and cerrado with scattered trees, bushes, dwarf palms, termite mounds and anthills (Pelzeln 1868, Collar et al. 1992, Clay et al. 1997, Lowen et al. 1997). Possibly favours areas that are regenerating after fires (Collar et al. 1992, Rodrigues et al. 1999), although further research is recommended (Capper et al. 2000).
Vocalization and behaviour: Crepuscular and nocturnal. Males give undulating whistles during territorial disputes or when alarmed. Females utter sharp, single notes (Cleere 1998).
In the breeding season, males perform short display flights from low termite mounds, during which they make rapid, wing fluttering sounds (Clay et al. 2000), the white wing and tail feathers being extremely noticeable. Roosts and nests on small patches of bare soil in cerrado or grassland, usually beneath overhanging grasses and plants. Appears to rely on crypsis less than other nightjar species, using nearby vegetation for protection during the day. Does not appear to sit on roads and tracks at night, but frequently uses low perches. When foraging, flight is often slow and interspersed with frequent glides. At other times, flight is strong and direct with a series of double wing beats and short glides.
Eggs: The first eggs of this species were discovered in Canindeyú, Paraguay on 22 November 1997 (Capper et al, 2000). As a result of intensive field studies, several nests have been found in the same region during the years 1998, 1999 and 2000 (Pople pers. comm.). The eggs are elliptical, 28.7 - 28.9 x 21.3 - 21.4 mm, have a buffish or creamy-brown ground colour and are finely spotted and scrawled grey, black and brown.
The Sickle-winged and White-winged Nightjars are two poorly known, Neotropical species that share similar morphological features, vocalizations, behavioural traits and habitat preferences. Both have restricted ranges, occurring in open grasslands in southern South America, generally where there are reddish soils. They are both sexually dimorphic. Males have cinnamon-tinged, cryptic plumages and lack the white mid-wing and outer tail markings typically found in the genus Caprimulgus. Females have a brownish, variegated plumage, although they do not appear to nest or roost on leaf litter. Males have curved primaries that, during territorial and courtship display flights, produce a flapping sound quite unlike the deliberate clapping given by many Caprimulgus nightjars, which have straighter primaries. The wings of the males have also evolved to different extremes. The Sickle-winged Nightjar has the strangest shaped wing of all nightjar species, and appears to have a sound-orientated display flight. The White-winged Nightjar has more white in the wing than any other species, and appears to have a more visual display. In between display flights, the males of both species give similar, soft, call notes, although descriptions of these vocalisations have yet to be published. The eggs of both species are rather similar, having a buffish ground colour with fine markings, and differ from those of most Caprimulgus eggs, which generally have a whitish ground colour and are boldly spotted and blotched. Both species also share the broader bill, proportionally longer rictal bristles and partially feathered tarsi, which further differentiate them from Caprimulgus nightjars.
The White-winged Nightjar is clearly not a Caprimulgus species and is probably a close relative of the Sickle-winged Nightjar. I propose that this species be moved into the genus Eleothreptus with the name White-winged Nightjar Eleothreptus candicans. This proposal is a shortened version of the paper by Cleere 2002.
Capper, D.R., Esquivel, E.Z., Pople, R.G., Burfield, I.J., Clay, R.P., Kennedy, C.P. & Mazar Barnett, J. 2000. Surveys and recommendations for the management of Aguará Ñu in the Reserva Natural del Bosque Mbaracayú, eastern Paraguay. Unpublished report.
Clay, R.P., Capper, D.R., Mazar Barnett, J., Burfield, I.J., Esquivel, E.Z., Fariña, R., Kennedy, C.P., Perrens, M. & Pople, R.G. 1997. White-winged Nightjars Caprimulgus candicans and cerrado conservation: the key findings of Project Aguará Ñu 1997. Cotinga 9: 52 - 55.
Clay, R.P., López Lanús, B., Tobias, J.A., Lowen, J.C. & Mazar Barnett, J. 2000. The display of the White-winged Nightjar. J. Field Orn. 71: 619 - 626.
Cleere, N. 1998. Nightjars. A guide to nightjars and related nightbirds. Pica Press, Sussex.
Cleere, N. 1999. Family Caprimulgidae (Nightjars). In: del Hoyo J., Elliott A. & Sargatal J. (eds) Handbook of the birds of the world Vol. 5.: 302 - 386. Lynx Edicions, Barcelona.
Cleere, N. 2002. A review of the taxonomy and systematics of the Sickle-winged and White-winged nightjars (Caprimulgidae). Bull. Brit. Orn. Cl. 122 (3): 168 - 179.
Collar, N.J., Gonzaga, L.P., Krabbe, N., Madroño Nieto, A., Naranjo, L.G., Parker, T.A. & Wege, D.C. 1992. Threatened birds of the Americas. The I.C.P.B./I.U.C.N. Red Data Book, Cambridge, U.K.
Davis, S.E. & Flores, E. 1994. First record of White-winged Nightjar Caprimulgus candicans for Bolivia. Bull. Brit. Orn. Cl. 114: 127 - 128.
Gould, J. 1838. A very singular form among the Caprimulgidae. Proc. Zool. Soc. London 1837: 105.
Gray, G.R. 1840. A List of the genera of birds with an indication of the typical species of each genus. R. & J. E. Taylor, London.
Ihering, H. 1902. Contribuições para o conhecimento da ornitologia de São Paulo. Rev. Mus. Paulista 5: 261 - 329.
Kirwan, G.M., Martuscelli, P., Silveira, L.F. & Williams, R.S.R. 1999. Recent records of the Sickle-winged Nightjar Eleothreptus anomalus in south-east Brazil. Bull. Brit. Orn. Cl. 119: 202 - 206.
Lowen, J.C. 1999. Um novo registro da reprodução de Eleothreptus anomalus (Caprimulgiformes: Caprimulgidae) para o Brasil. Ararajuba 7: 139.
Lowen, J.C., Clay, R.P., Barnett, J. M., Madroño, N. A., Pearman, M., Lanús, B. L., Tobias, J. A., Liley, D. C., Brooks, T. M., Esquivel, E. Z. & Reid, J. M. 1997. New and noteworthy observations on the Paraguayan avifauna. Bull. Brit. Orn. Cl. 117: 275 - 293.
Miatello, R, Cobos, V. & Rosacher, C. 1991. Algunas especies de aves nuevas o poco conocidas para la provincia de Córdoba, República Argentina. Hist. Nat. 8: 1 - 5.
Pearman, M. & Abadie, E. 1995. Field identification, ecology and status of the Sickle-winged Nightjar Eleothreptus anomalus. Cotinga 3: 12 - 14.
Pelzeln, A. 1868. Zur Ornithologie Brasiliens Pt. 1. A. Pichler's Witwe und Sohn, Wien.
Pereyra, J.A. 1950. Avifauna Argentina. Hornero 9: 178 - 241.
Rodrigues, F.H.G., Hass, A., Marini-Filho, O.J., Guimarães, M.M. & Bagno, M.A. 1999. A new record of White-winged Nightjar Caprimulgus candicans in Emas National Park, Goiás, Brazil. Cotinga 11: 83 - 85.
Straneck, R.J. & Viñas, M.J. 1994. Comentarios sobre costumbres y manifestaciones acusticas del atajacaminos de los pantanos, Eleothreptus anomalus (Gould 1838) (Aves, Caprimulgidae). Notulas Faunisticas 67: 1 - 4.
Nigel Cleere, January 2007
Additional note from Remsen: Barrowclough et al. (2006) [see our SACC bibliography -- I have pdf I you need one] found that Caprimulgus is highly polyphyletic, with none of the New World species related to true Caprimulgus of Old World, and New World "Caprimulgus" themselves not a monophyletic group; unfortunately, they didn't have samples of candicans or anomalus.
Comments from Stiles: "A tentative NO, for now. Cleere is quite likely right, but given the obviously unsettled state of generic-level taxonomy of the New World Caprimulgus following the Barrowclough et al. study, I would prefer to await more information including a genetic study with more comprehensive taxon sampling. Given the lack of genetic data on these two species and the strong sexual selection likely behind their distinctive characters, there exists the possibility that they may be best included with other species in a different genus, or turn out not to be sister species.... hence better to wait on this one."
Comments from Zimmer: "YES". Gary's point about waiting for a molecular-based refinement of New World Caprimulgus is well taken, and part of me is tempted to vote NO for that reason. I do think that a molecular-based phylogeny will result in more (potentially drastic) shuffling in this group. That said, I don't think it hurts to move in a particular direction based on evidence available at the time, even if it means revisiting the issue later. As Nigel Cleere points out, there a number of characters that would seem to unite candicans and anomalus, and until we see molecular evidence to the contrary, I'm willing to go in this direction."
Comments from Nores: "NO. Aunque el análisis de Cleere me parece muy bueno y los aspectos marcados me parecen bastante convincentes, no estoy convencido de que sean congenéricos. La aclaración que hace Cleere en el primer párrafo de que el diseño de las plumas del ala puede haber evolucionado de un display territorial y cortejeo y que posiblemente no constituye un carácter genérico tiene para mi poca base, y por medio de ese análisis elimina uno de los caracteres más importantes del género. Pienso que este es un caso que necesita especialmente un análisis genético."
Comments from Cadena: "YES. The reasoning presented by Cleere is convincing, and although taxon sampling across the family is not great, a recent study based on cytochrome b sequence data (Larsen et al. 2007 Molecular Phylogenetics and Evolution 42: 789-796) placed anomalus and candicans as sister taxa, forming a strongly supported clade that excludes Caprimulgus longirostris, C. maculicaudus, C. vociferus, C. inornatus, C. europaeus, C. climacurus, and C. fraenatus. Importantly, europaeus is the type species of Caprimulgus. Considering the rampant polyphyly of Caprimulgus shown by recent studies (including a recent master’s thesis by Kim Han that hasn't been published but has good taxon sampling, fide Mike Braun), this seems like a logical first step in the right direction."
Comments from Robbins: "NO, although it is likely that candicans is sister to anomalus, a robust, unpublished molecular data set (Kin-Lan Han et al.) demonstrates that the genus Eleothreptus, as well as a few other genera, will need to be subsumed into another genus that has priority. Kin, Mike Braun, and I plan to soon submit these results for publication. Thus, there is no point in making this change when both of these taxa will have to be transferred to another genus."
Comments from Jaramillo: "YES - The Cleere analysis I buy, and the other non-sexually selected features he notes (feathered tarsi etc.) are good indicators that he is probably right in suggesting a sister relationship between these two taxa. My huge hesitation is due to the comment by Robbins, but on the other hand, we can only act on data that is out there already. I see no reason to accept this more favorable (than keeping candicans in Caprimulgus) arrangement for now, and re-assess when new data is published. It can take so long for data to finally get out there, that I would rather act on something now, than wait. Call me impatient."
Comments from Remsen: NO. The sister relationship looks solid, but if the two Eleothreptus make one of the newly constituted New World genera (ex-Caprimulgus) paraphyletic, then we will have to reverse the decision."