The Condor 91:193-197 0 TheCooper Ornithological Society 1989 THE SILKY-TAILED NIGHTJAR AND OTHER NEOTROPICAL CAPRIMULGIDS: UNRAVELING SOME MYSTERIES’ JOHN WILLIAM HARDY Department of Natural Sciences, Florida Museum of Natural History, University of Florida, Gainesville, FL 3261 I ROBERTO STRANECK Laboratorio de Sonidos Naturales, Museo Argentinas de Ciencas Naturales, Angel Gallardo 470-1405, Buenos Aires, Argentina Abstract. The Silky-tailedNightjar, Caprimulgus sericocaudatus, is identifiedby song fromYarinacocha, Ucayali, Peru, and from Misiones Province, Argentina. Two caprimulgids of Yucatan,Mexico and adjacentareas, C. badius and Nyctiphrynus yucatanicus, are shown to have almostcertainly had their songsconfused with eachother by field ornithologists. By transposingtheir songs,the songsof eachspecies then more closelyresemble the songs of their presumedclose relatives. Thus, the ree-o-ree song of C. badius closelyresembles the songof C. sericocaudatus and the will songof N. yucatanicus resemblesthe songsof N. mcleodii and N. ocellatus. The chip-willow songof C. salvini is shownin a sonogramto be a temporallycondensed version (with similarfrequency modulation) of the songof C. badius and C. sericocaudatus, its presumedclose relatives. It is hypothesizedthat the ree-o-ree song is primitive and the chip- willow songderived. Key words: Nightjars; Caprimulgidae; vocalizations; systematics. INTRODUCTION under ideal conditions for finding the bird, but Nightjars (Caprimulgidae) are confusingly sim- could not find it. John Fitzpatrick (in litt. to ilar to one another in color pattern, usually re- Hardy) pointed out that two specimens of the sembling the terrestrial substrateupon which they Silky-tailed Nightjar, Caprimulgus sericocauda- rest hidden by day. Becausethey are largely noc- tus, had been collectedat Yarinacocha (seeTray- turnal, their habits are poorly known compared lor 1958, concerning the first of these)and wisely to those of many birds. Ornithologists have, in suggestedthat the mystery voice might be the the past three decades,concentrated on recording song of this species.This possibility is discussed and study of nightbird voices in the hope of find- in Hardy (1985). The Silky-tailed Nightjar is one ing clues to relationships among forms (see, for of the lesser known Neotropical caprimulgids, example, Marshall 1978). On 7 October 1983, ranging from easternPeru to northern Argentina. at Yarinacocha, Ucayali, Peru, Ben B. Coffey, Jr. Most of the few museum specimens are from tape-recorded the voice of an unidentified cap- Misiones Province, in extreme northern Argen- rimulgid. Hardy (1980, 1986) subsequently con- tina. Until 1986, its voice had never been de- cluded that the voice might be that of a new scribed. Among ornithologists, the voice was species,and suggestedthat it could be an Otoph- known perhaps only to the late William Par- anes (=Nyctiphrynus, see AOU 1983) because tridge, who located the birds by their song and its ree-o-ree song resembled the song attributed collected them in Misiones Province (K. C. at that time to the Yucatan Poorwill, Nyctiphry- Parkes, in litt.). nus yucatanicus. That resemblance can be heard in Hardy (1980, 1986) and Hardy et al. (1988) SILKY-TAILED NIGHTJAR VOICE as well as seen in Hardy (1985) and in Figure 1 CONFIRMED in this paper. Straneck heard Hardy’s published nightbird re- Hardy and Coffey returned to the place of the cord and tape (1980, 1986) and recognized the latter’s recording of the mystery bird in 198 1, mystery voice as similar to a night song he had heard in Parque National Iguazu, Misiones on 26 August 1982. In November 1986, at Urugua-i I Received5 July 1988.Final acceptance28 Septem- Misiones, 30 km SW of Bernard0 de Irigoyan, ber 1988. he tape-recorded the mystery bird and also col- 11931 194 JOHN WILLIAM HARDY AND ROBERTO STRANECK FIGURE 1. Sonogramsof advertising songsof certain nightjars, genus Caprimulgus.a. Caprimulguss. seri- cocuudutus.Arroyo Urugua-i, 30 km SW of Bernard0 de Irigoyen, Misiones, Argentina. 16 November 1986. R. Straneckcollection (copy in Florida Museum dub file). b. Caprimulgussericocaudatus mengeli. Yarinacocha, Ucayali, Peru. 7 October 1973. B. B. Coffey, Jr. BBC collection (copy in FM dub file). c. Caprimulgusbadius. 6.2 km N Hopelchen, Campeche,Mexico. 28 April 1966. B. B. Coffey, Jr. (copy in FM dub file). d. Caprimulgus salvini. Tanunul near Valles, San Luis Potosi, Mexico. 24 April 1964. B. B. Coffey, Jr. collection (copy in FM dub file). Sonogramsproduced on a Kay Elemetrics Sona-Graph model 7029A, employing the 4w,OOO Hz frequency spectrum and 300 Hz band filter. lected the singer. It was a Silky-tailed Nightjar. neck compared to Hardy’s recollection of the The songs of the Argentine and Peruvian birds Peruvian habitat. (Fig. la, b) differ slightly, probably due to geo- graphic variation. Dickerman (1975) described YUCATAN CAPRIMULGID VOICES and named the northern population of this species TRANSPOSED? as a new, smaller, darker race, C. s. mengeli. This Yet a puzzle remained: why should this Capri- race, based on voice comparison here (Fig. l), mulgus speciessound like a Nyctiphrynus of Yu- has a noticeably higher-pitched sound and a catan, Mexico? Recent observations by Jan Pier- longer tonal glissconnecting the two major pitch son, Rose Ann Rowlett, and Bret Whitney peaks of its utterance (hear this difference in (Pierson 1986) seem to offer a solution. Because Hardy et al. 1988). The Argentine bird had been Pierson’s paper is not easily available, we sum- singing in the thicket edge of forest, similar to marize it here in greater detail than we would the habitat where Coffey had made his recording otherwise. in Peru, judging from photographstaken by Stra- First, there are two nightjars in the Yucatan NEOTROPICAL NIGHTJARS 195 a b c FIGURE 2. Sonogramsof advertising songsof certain nightjars,genus Nyctiphtynus. a. Nyctiphtynusocellatus. Explorer’s Inn on Rio Tambopata, Madre de Dios, Peru. 16 June 1978. B. B. Coffey, Jr. collection (copy in FM dub file). b. Nyctiphrinusyucatanicus. 2.5 km N Uxmal, Yucatan, Mexico. 25 March 1976. B. B. Coffey, Jr. collection (copy in FM dub file). c. Puerto Los Marzos, W of Autlan, Jalisco, Mexico. 1 March 1965. B. B. Coffey, Jr. collection (copy in FM dub file). See Figure 1 for sonogram analysis parameters. (B. B. Coffey recordings,now in the FM dub file, will eventually be cataloguedin the master tape file.) Peninsula (excluding two speciesof Chordeiles- cording of the will song. A bird hew in and he nighthawks), the Yucatan Poorwill, N. yucatan- illuminated it with a 200,000 candle-power spot- icus, already mentioned (it is also in Guatemala) light. It was a N. yucatanicus. It did not call or and the Yucatan Nightjar, C. badius, considered sing and the will song, initially heard, ceased, by the AOU (1983) to be a race of C. salvini, the indicating that he had attracted the singing bird. Tawny-collared Nightjar. The grounds for con- Driving farther down the road, he stopped again sidering it a distinct speciesare its reported song, where a ree-o-ree song could be heard. Here he which has been onamatopoeically rendered as played the ree-o-reesongand some chuckingcall- will, will, will, etc., compared to the chip-willow, notes that ree-o-ree singers often give. When a chip-willow, chip-willow, etc. of nominate C. sal- bird approached and was spotlighted, it proved vini of adjacent eastern tropical Mexico. In any to be a C. badius! Meanwhile, no ree-o-ree sing- case, published works (e.g., Peterson and Chalif ing was audible in the distance, leaving no doubt 1973) that discuss songs of the two Yucatan- in Pierson’s mind that the ree-o-ree songswere inhabiting nightjars statethat N. yucatanicussings those of the C. badius. ree-o-ree and C. badius sings will, will, will. Pierson also reports that Rowlett has heard On the night of 26 March 1986, near Uxmal, that ree-o-ree songon Cozumel Island (off main- Yucatan, Pierson heard the will songcoming from land Yucatan) where only C. badius (and not N. low dry scrub vegetation. He played a tape re- yucatanicus)has been collected. Furthermore, he 196 JOHN WILLIAM HARDY ANIJROBERTO STRANECK writes, Whitney has heard only the will song at gestion of a tawny collar and C. badius has a the Tikal Ruins, Peten, Guatemala, where, of well-defined, continuous tawny collar. Capri- thesetwo nightjars, only N. yucatanicusis known mulgussericocaudatus is a larger bird, very sim- to occur. Quoting Pierson: “Both of these audio ilar in plumage to its northern relatives, but lack- identifications would have been first records for ing a collar. both species in these areas according to tradi- Having here presentedevidence that vocaliza- tional vocal identifications. However, if the tions may correlate well with other perceived vocalizations are switched, these records fall evidence of relationships, we were puzzled that nicely into accord with the species’ ranges.” while the ree-o-ree songs of C. badius and C. While final proof of what these observations sericocaudatussuggest close relationship, the chip- indicate will perhaps rest on recordings of each willow song of C. salvini seemed, to our ears, to species’ songfollowed by collecting of the singers, do no such thing. Sonograms (Fig. lb, c), how- it seems likely that ornithologists have simply ever, show that the chip-willow song of C. sal- been confusing the songs of the two. The con- vini is a rapidly uttered, temporally condensed fusion seems to date from the earliest mention version of the same sort of frequency modula- that we can find of voice in both these forms. tions that comprise that configuration of the ree- Davis (1962) discussesthe song of N. ocellatus o-ree song of C. badius and C. sericocaudatus- and for it showsa sonogramof the ree-o-reesong. the inverted “V” followed by the “M.” Davis (1972) treats also the will song assigning We suggestthat the ree-o-ree songsshared by it to C.