Little known Oriental bird: Heinrich's Nightjarby Iwein Mauro, from OBC Bulletin 37, June 2003. Walking down from the dismantled Anaso logging camp on the western slopes of Mount Rorekatimbu towards the Palu-Napu main road bisecting the Lore Lindu National Park in Central Sulawesi around dusk on 18 July 1998, I was truly startled by an unidentified flying object nearly colliding with me. Probably as shocked as I was, it hovered for a few seconds at breast height less than half a meter in front of me whilst repeatedly uttering a distinctive tchor and subsequently perched nearby at eye-height on top of low roadside ginger thickets, soon revealing itself as a medium-sized nightjar Caprimulgus species. Fortunately this bird remained happily in the torch beam for about five minutes as I gradually approached it down to point-blank range and I had little hesitation in identifying it as a female Heinrich's Nightjar Eurostopodus diabolicus, one of Sulawesi's most enigmatic and sought-after endemic bird species (overview in Birdlife International (2)).
On 23 July I revisited the site, which is situated at about 1,900 m elevation, accompanied by Bernard and Erika Van Eleghem-Winne, who had received a sound recording of E. diabolicus secured by Mark Van Beirs also at Anaso during a Birdquest the previous year, de facto perhaps the first definite contemporary record of the species (see below). Most likely the territorial male belonging to the previously spotted female, responded dramatically for a short period around dusk by flying several times low overhead and calling back regularly. Between 15 and 18 December 1998 together with Raf Drijvers I taped out a pair on three occasions around the former Anaso clearing at about 2,000 m elevation and further located two different pairs along the main road at an altitude of about 1,750 m near Lake Tambing.(1,2) With the exception of the Anaso pair, which perched briefly though rather distantly, the birds were mostly seen in flight, however they allowed for their vocalisations to be sound recorded. On 13 July 2000 I heard and briefly saw what was undoubtedly Heinrich's Nightjar in ridgetop lower montane forest at 1,650 m within the Gunung Ambang Nature Reserve, Bolaang Mongondow, North Sulawesi. Great Eared Nightjar Eurostopodus macrotis constitutes the prime confusion species and numerous unsubstantiated claims of Heinrich's Nightjar persist, originating from the fact that few observers seem to realise that the subspecies macropterus endemic to Sulawesi is strikingly different from the huge harrier-like E. m. cerviniceps of mainland South-East Asia that they have usually become acquainted with previously. It definitely remains odd that many observers claiming diabolicus actually do not see Great Eared Nightjar at all on Sulawesi despite the latter's generally much greater relative abundance. Coates and Bishop(3) briefly summarised the main distinguishing features of Heinrich's Nightjar and the species' identification has been thoroughly elucidated by Cleere and Nurney.(4) In contrast, Bishop and Diamond5 incomprehensibly perpetuate some of the previously reigning misconceptions by talking about a much larger E. m. macrotis with harrier-like flight when discussing differences with diabolicus. Only the unique female type specimen of Heinrich's Nightjar exists and there are slight discrepancies in available published measurements. Based on those provided by Cleere and Nurney4 and under the assumption that sexual biometric differentiation within diabolicus is marginal, as in the closely allied Archbold's Nightjar Eurostopodus archboldi of montane New Guinea (see below), estimated size disparity between the two forms could be up to about 20% in total body length, 26% in wing length and about 20% in tail length. Naturally, some caution is appropriate given that only the holotype is available for analysis and in other members of Eurostopodus the male is known to be the larger sex, in which case the discrepancies may be even further reduced slightly. Nonetheless figures above are consistent with my personal live perception of both taxa and although substantial, to the inexperienced observer such differences may, however, not always be easy to assess correctly in the field, especially in the dim light conditions that characterise many nightjar sightings. |
