Little known Oriental bird: Heinrich's Nightjar: 2by Iwein Mauro, from OBC Bulletin 37, June 2003. Sulawesi Nightjar Caprimulgus celebensis and Savannah Nightjar C. affinis share with diabolicus a similar biometry, making flight identification without additional supporting evidence problematical. (4) It should be fairly straightforward that the former taxon's imperfectly known, allegedly fragmentary distribution on Sulawesi is likely to reflect inadequate coverage rather than genuine ecological and distributional processes and whilst it may be argued that the latter, due to its different habitat requirements, not normally coexists with diabolicus, both these species at all times require earnest consideration during identification. On Sulawesi, Great Eared Nightjar appears more attenuated, slimmer and obviously longer- and stiffer-winged, with a more pointed hand resulting in a leisurely, buoyant and purposeful flight mode with frequent long and steady glides and only occasional fluttering when actually feeding. It is a typically aerial feeder, usually hunting above the forest canopy and sometimes congregating in loose flocks of up to about 10 birds when actively feeding. However, on several occasions I have also observed this species feeding singly or in pairs very low above the ground in a manner highly reminiscent of diabolicus. Heinrich's Nightjar is a rather compact, short-tailed, short- and noticeably blunt-winged species, with rapid, fluttering wing beats and an erratic flight only interspersed by short sweeping glides, that forages singly or in pairs and nearly always keeps very low to the ground. In fact, I have personally never observed diabolicus flying higher than mid canopy (contra Bishop and Diamond (5)). As noted for Archbold's Nightjar(4) (and pers. obs. author), this species also catches prey by repeatedly sallying from exposed branches situated low above the ground in small clearings or from atop roadside thickets (pers. obs. author). In summary, Heinrich's Nightjar plumage-wise is best identified
on the combination of One apparently previously overlooked, though diagnostic feature, readily allowing identification under very poor conditions is that the eyes of Heinrich's Nightjar consistently glow purplish in the spotlight (pers. obs. author; pers. com. R. Drijvers; pers. com. M. Van Beirs; co ntra Bishop and Diamond (5)) while those of Great Eared Nightjar, at least on Sulawesi, reflect yellowish and Sulawesi Nightjar's shine bright red. I feel this is a very reliable feature and for that reason suggest that Bishop and Diamond's rediscovery of Heinrich's Nightjar(5) be treated with the necessary caution. A conclusion reinforced by the fact that the described behaviour of the birds does not fit in with my knowledge of the species and that provided plumage details are rather crude and unconvincing. R. Drijvers and I originally noticed that one member of the territorial pair observed repeatedly, though briefly, in December 1998 (see above), displayed relatively extensive whitish markings in the outer wings. Images recently made available equally strongly suggest that E. diabolicus is sexually dimorphic, sexes varying at least in the amount of white in the outer primaries and colouration and patterning of the lower scapulars. Presumed males exhibit whitish elongated spots on P2–5 (numbered ascendantly) and relatively plain, mainly greyish, indistinctly patterned lower scapulars forming a pale panel, whilst females have the whitish in the wing restricted to exceedingly small spots on P3–4 and buffish lower scapulars boldly vermiculated with dark brown. Additional work is necessary to gain further insight into this taxonomically significant issue. The male advertising call is highly distinctive and may best be transcribed as a loud, somewhat bubbling series of up to 36 kweik notes, more or less delivered at constant pitch and speed and lasting about 4.7 seconds. Contact calls include a soft, mellow wheet, often quickly repeated up to three times, and distinctive, rolling kreep notes uttered at variable pitch. Calls are given very infrequently and perhaps mainly around dusk. Around this time the species may respond dramatically to tape playback by repeatedly calling back and by flying back and forth, often passing overhead at very close range. However at other times of night birds proved surprisingly lethargic and no reaction was noted at all. All evidence suggests that the species calls exclusively in flight. When agitated, as the bird that nearly flew against me was, a guttural, churring tchor is uttered repeatedly. I stress here that none of these vocalisations are consistent with those previously tentatively ascribed to the species. (2,5,6) Clearly the affinities of Heinrich's Nightjar lie with the Australopapuan members ofEurostopodus and definitely not with the truly eared, Oriental species – which should perhaps be retained in a separate genus Lyncornis 4 – and the absence of Eurostopodus from the Moluccas and Lesser Sunda islands chain remains puzzling in this respect. Pending further study into the intrageneric limits of Eurostopodus, I therefore recommend continued use of the vernacular name Heinrich's Nightjar (3,4) over Sulawesi Eared Nightjar (2). The presence of white spots on the outer primaries in both sexes of diabolicus, constitutes a highly significant feature, suggesting it groups with the Spotted E. argus and White-throated Nightjar E. mystacalis. However these species exhibit many morphological characteristics that are not attributable to Heinrich's Nightjar, produce highly divergent vocalisations and have different ecological requirements, comprising essentially non-forest species.(4) During opportunistic bird surveys in the Arfak mountains, Vogelkop peninsula, Papua (formerly Irian Jaya) province, Indonesia I learned that the local population of the closely related Archbold's Nightjar E. archboldi there – only discovered as recently as 19957 more than 600 km away from its nearest known breeding grounds in the Snow mountains, Papua province, Indonesia – exhibits exceedingly similar advertising calls to those of diabolicus. I failed to sound record archboldi in the Arfaks though readily lured and caught two different individuals in a mist net with a recording I had made of diabolicus. Given this vocal analogy and many similarities in external morphology including sexual dimorphism, it might perhaps be argued that Archbold's Nightjar is the closest living congener of diabolicus. Archbold's Nightjar too remains a noticeably poorly known taxon: the westernmost boundary of its distribution along New Guinea's central cordillera is imperfectly known and in its historic range its vocalisations remain to be adequately described and documented4 (and B. Beehler in litt., 24 January 2002). That Heinrich's Nightjar – until recently known only from foothills at approximately 250 m elevation at the base of Mount Klabat in the Minahassa peninsula of North Sulawesi – should now suddenly be regularly encountered in montane forest up to at least 2,000 m (pers. obs. author) more than 750 km away from the type locality, strongly suggests that the species ranges widely across forested Sulawesi and occupies a broad altitudinal zonation. Taking its retiring, crepuscular and nocturnal habits and generally silent nature into account E. diabolicus is probably greatly overlooked rather than rare and is quite likely at least locally reasonably common. Furthermore, as it appears to be partly tolerant to habitat degradation, its treatment as Vulnerable 2,8 may perhaps be downgraded to Near-threatened. Acknowledgements References
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