Circaetus gallicus sacerdotis

Ng, Nathaniel S. R., Christidis, Les, Olsen, Jerry, Norman, Janette & Rheindt, Frank E., 2017, A new subspecies of Short-toed Snake-eagle from Wallacea determined from morphological and DNA comparison, Zootaxa 4358 (2), pp. 365-374 : 371-372

Circaetus gallicus sacerdotis , subspecies nova; LES CHRISTIDIS, NATHANIEL S.R. NG, JERRY OLSON, JANETTE NORMAN, FRANK E. RHEINDT

Holotype. We designate specimen 81114 from Naturalis, Leiden (formerly the Rijksmuseum van Natuurlijke Historie) as the holotype ( Fig. 2 ). The individual is an adult male collected from Nunang, Flores, by Erwin Schmutz on 20 January 1973. The holotype is a medium-sized snake eagle of the same general shape as Short-toed Snake-eagles from the Palearctic, and with a dark greyish-brown head and breastband. The rest of the breast and belly are white with brown spotting. Based on measurements taken by Mees (1975), the wingspan is 530 mm and tail length is 268 mm.

Etymology. The name sacerdotis , the genitive singular of the Latin word for “priest”, honours the singular achievements of the holotype’s collector, Father Erwin Schmutz, in the ornithological exploration of Nusa Tenggara in general and Flores in particular. Father Schmutz (born 1932) arrived on Flores in 1963 as a missionary and remained for many years, during which he contributed greatly to the collection of bird specimens from this island.

Diagnosis. Circaetus gallicus sacerdotis is generally smaller in size than C. gallicus gallicus . In C. g. sacerdotis , wingspan ranges from 507–530 mm in males (n= 5) and 510–519 mm in females (n=2), whereas in C. g. gallicus it ranges from 520–550 mm in males (n=8) and 530–580 mm in females (n=6) ( Table 3 ). In C. g. sacerdotis , tail length ranges from 259–275 mm in males (n=4) and 264 mm in females (n=1), whereas in C. g. gallicus it ranges from 272–274 mm in males (n=2) and 286 mm in females (n=1). At a minimum in females, C. g. sacerdotis is paler and less barred and spotted than C. g. gallicus , with pale brown droplets and speckling on white underparts.

Distribution. C. g. sacerdotis is a resident in the Lesser Sunda islands of Lombok, Sumbawa, Komodo, Flores, Pulau Besar, Alor, Pantar, Sumba, Rote, Wetar, Tanimbar and Timor (Eaton et al. 2016; Trainor et al. 2009). Records of its presence between April and December in Baluran National Park suggest that it is possibly a nonbreeding visitor to East Java and Bali from the Lesser Sundas (van Balen & Compost 1989, Winassis et al. 2011). Its habitat, summarized in Coates & Bishop (1999) and Eaton et al. (2016), is primary and tall secondary monsoon woodland, savannah woodland, mixed scrub and lightly wooded cultivation.

Origins and conservation implications. Mees (2006) suggested that the Lesser Sundas form of C. gallicus could have arrived during the Late Pleistocene, when changes in climate and vegetation cover resulted in the formation of drier habitat corridors for these eagles. This scenario is supported by more recent paleoclimatological data indicating that recurring glaciations during the late Pleistocene would have led to savannah corridors connecting monsoonal areas of mainland Southeast Asia with Java and Bali across land bridges ( Wurster et al. 2010). This would have allowed eagles to disperse from their main Palearctic and Indian range to similarly monsoonal areas in southern Wallacea. Our DNA data are consistent with such a scenario: using an approximate molecular clock of 2% mitochondrial divergence for coding genes per million years ( Quinn 1997; Lovette 2004; Weir & Schluter 2008), divergence time between sacerdotis and the nominate populations dates around 200,000 years ago, which marked the beginning of the antepenultimate global ice age.

Therefore, C. g. sacerdotis has been an integral part of the ecosystem and biota of the Lesser Sundas as one of the top endemic predators throughout the Holocene and latest Pleistocene. According to Coates & Bishop (1999), C. gallicus is an uncommon resident in the Lesser Sundas that is locally moderately common on Alor, Flores and Timor, but field data from the last 10 years indicate that populations have decreased substantially, with many fewer sightings as compared to the early 2000s (FER pers. obs.; J.A. Eaton, pers. comm., February 2016). Human population increases and accompanying habitat loss could be a major factor behind this decline: the total human population of East Nusa Tenggara increased by 11% in just six years between 2010–2016, with further increases expected (Badan Pusat Statistik Provinsi Nusa Tenggara Timur 2017). Overcollection for the captive bird trade is also likely to be a contributing factor, and has been identified to be a major factor behind the decline of another Indonesian raptor, the Javan Hawk-eagle Spizaetus bartelsi Stresemann (van Balen et al. 2000) . Having now established that C. gallicus sacerdotis actually represents a distinctive subspecies, its conservation status needs to be re-evaluated. If Flores, Alor, Sumba and Timor are its stronghold then human pressures will be a threat as these islands are major growth areas in the region.

Figures

FIGURE 2. Boxplots of wingspan and tail lengths across both sexes in Lesser Sundas Short-toed Snake-eagle populations as compared to Palearctic populations. The boxes mark out the 25th–75th percentiles. Palearctic birds are consistently larger than individualsfrom the Lesser Sundas.Additionally, in Palearctic populations females arelarger thanmales,whereas in the Lesser Sundas populations, female-biased dimorphism is absent, both sexes being of similar size.