Cyornis omissus omississimus, Rheindt & Prawiradilaga & Ashar & Lee & Wu & Ng, 2020

Rheindt, Frank E., Prawiradilaga, Dewi M., Ashar, Hidayat, Lee, Geraldine W. X., Wu, Meng Yue & Ng, Nathaniel S. R., 2020, A lost world in Wallacea: Description of a montane archipelagic avifauna (supplement), Science 36, pp. 1-104 : 57-63

SM9:

Cyornis omissus omississimus , subspecies nova

(Togian Jungle-Flycatcher;

urn:lsid:zoobank.org:act:3A22FC10-1310-4394-AC6A-4FE86125A4ED

) Frank E. Rheindt, Dewi M. Prawiradilaga, Hidayat Ashari, Suparno, Chyi Yin Gwee

Holotype

MZB.Ornit.34.483 ( fig. S13 ); adult male collected 26 Dec 2013 at Dolomino Forest (~ 150m) near Tanimpo village, desa Wakai, island of Batudaka, Togian Archipelago (S 00⁰ 26.042 '; E 121⁰ 51.357 '). Collected by the Rheindt / LIPI field party, including tissue samples from breast muscle and liver; skin prepared by Suparno; field number Tog09; no body and wing molt; low fat; weight 17.5g; wing length 7.5cm; wing spread 22cm; total length 14cm; bill 1.4cm; tail 6.1cm; tarsus 1.8cm.

Description of holotype

Lower forehead and narrow supercilium iridescent blue (5PB 5/10), grading out behind eye; crown and mantle darker, duller blue (7.5PB 2/10); lores and chin black grading into blackish-blue (7.5PB 1/2) on sides of face and sides of throat; large brilliant iridescent blue carpal patch concolorous with or slightly paler than supercilium; rest of wing as mantle, with outermost remiges becoming increasingly blackish; rectrices blackish on both sides, grading into a subdued ultramarine blue (2.5PB 3/4) from inner towards outer webs on upper side; throat orange-rufous (7.5YR 7/10) grading into darker, more chestnut hue on centre of breast (5YR 4/8) and back into throat color towards lower underparts, with a slightly paler center of belly and vent (7.5YR 7/8); breast sides dark blue (7.5PB 2/6); bill entirely black, iris very dark brown; tarsi, toes and claws in life greyish-horn with paler yellowish soles.

Diagnosis

Taxonomic treatment in this publication follows the latest classification of Cyornis flycatchers by Gwee et al. (7 4). The new Cyornis omissus omississimus is a mid-sized jungle - flycatcher with dark blue upperparts and rufous-chestnut underparts, obviously belonging to the Mangrove Jungle-Flycatcher C. rufigastra radiation, and within it clearly assignable to the geographically adjacent Sulawesi Jungle-Flycatcher C. omissus .

In bare parts, the consistently darker tarsi, toes and claws of both sexes distinguish this new subspecies not only from C. omissus omissus (Sulawesi) , but also from C. rufigastra rufigastra (Malay Peninsula, Sumatra, Borneo), C. r. longipennis (Karimunjawa Island), C. r. rhizophorae (Java, Bangka, Belitung) and C. r. karimatensis (Karimata Island).

In plumage, the all-rufous underparts of both sexes of C. o. omississimus distinctly differ from the extensive white belly and throat of C. kalaoensis , the white throat of C. omissus djampeanus , and the white bellies of Philippine subspecies of C. rufigastra (mindorensis, simplex, marinduquensis, philippinensis). Both sexes of the new taxon also differ from most remaining subspecies of C. rufigastra (including rufigastra , rhizophorae, longipennis and karimatensis) in their less pale, more intensely rufous belly.

The male differs from C. omissus omissus , C. o. peromissus (Salayar Island), C. rufigastra longipennis , C. r. rufigastra , C. r. rhizophorae and C. r. karimatensis in his broader, blacker face mask resulting in a narrower orange-rufous throat strip. The female differs from C. o. omissus and C. o. peromissus in her darker, richer blue upperparts lacking any strong brownish or greyish suffusion (including on auriculars) and contrasting more with the throat, and in her slightly greater extent of rufous (admixed with dark speckling) on the front of the face. The female also differs from C. r. rufigastra , C. r. karimatensis , C. r. longipennis , and C. r. rhizophorae in her more brilliant blue upperparts and rufous, less extensive (not white and more extensive) loral area, which does not wrap around the bill base in the new taxon.

Etymology

The names of two other subspecies, nominate C. o. omissus (Hartert, 1896) (‘neglected’ or ‘omitted’) from Sulawesi and C. o. peromissus Hartert, 1920 (‘extremely neglected’) from Selayar Island, were based on the impression that the description of these birds had escaped the attention of researchers for too long. The presently described taxon, only discovered in the 21 st century, fulfils that criterion even more adequately, so we take pleasure in naming it omississimus (‘the most neglected’), superlative of ‘omissus’.

Individual, sex and age-related variation within the taxon

The immature plumage remains undocumented. The only two male specimens known to exist (holotype and MZB.Ornit.34.488) show minimal plumage variation, the only difference perhaps being the latter specimen’s slightly brighter, more brilliant rump and darker, more blackish tarsus and claws in life.

As compared to males, the three female specimens have a duller blue supercilium (but still discernible), lack a black chin, have prominent rufous spectacles over a narrow blackish stripe through the cere, the rufous continuing to the lower sides of the face where it is finely speckled dark (in two of three females the speckling continues to the throat sides), and have much less dark blackish-blue auriculars, contrasting less with the rufous throat. The female’s upperparts are less brilliant blue. One of the three female specimens is slightly paler on the tarsus and claws.

History of discovery

The new subspecies was first reported by Indrawan et al. (13 3), who documented the sighting of a female on 15 May 2001 and a male on 29 July 2001 at 50-100m elevation around Benteng on the main island of Togian, and pointed out that this new population may be an undescribed subspecies. Following their footsteps, Filip Verbelen (pers. comm.) made the first sound recordings of the new population in December 2008 when studying a few individuals on Kadidiri, a tiny forested tourist resort island off the coast of Togian measuring ~4km in length and less than 1km in width. A few days later, F. Verbelen moved to Batudaka, one of the three main islands of the archipelago, where he found additional individuals in coastal forest near the capital town of Wakai. FER visited Batudaka Island from 23-27 April 2009 and observed this new population. On our collecting trip, we visited Batudaka from 24-28 Dec 2013 and found this taxon to be common in the forests outside the capital town of Wakai, collecting the present material in the process ( 19).

Distribution and status

The new subspecies is known from the Togian Archipelago in the Gulf of Tomini, a satellite group of islands between the northern and eastern peninsulas of Sulawesi. More specifically, to the best of our knowledge the new subspecies has so far been found on the two main islands of Togian and Batudaka, as well as on the tiny islet of Kadidiri off Togian, where it is common in remnant forest and edge from near sea level to at least ~200m elevation. However, it is likely that the birds occur up to the highest elevations at ~430m on these islands. More field research is required to map this subspecies’ occurrence on other islands in this archipelago. Its presence on some of the larger, forest-covered islands in close proximity to Batudaka and Togian, such as Talatakoh, Waleakodi and Waleabahi, is virtually guaranteed, given its occurrence on tiny Kadidiri. However, its presence on slightly more distant islands, such as Puah (at ~18km from the main archipelago) and Unauna (at ~28km from the main archipelago) is less certain, although these latter islands are connected to the main archipelago by shallow sea-beds not exceeding 120m depth, indicating that they would have been connected with one another during glacial sea level recessions.

On the main island of Sulawesi, the newly described omississimus is replaced by the nominate taxon omissus . Unusually, however, the nominate form on Sulawesi is a hill and montane forest denizen, occurring from 500-2300m elevation and shunning lowland forest habitats in stark contrast to the new subspecies.

The new subspecies appears to be moderately tolerant to habitat disturbance where small-scale timber extraction leads to a secondarization of primary forest. However, the taxon disappears where forest is converted into agricultural land. Although Togian’s forests are quickly dwindling, with most remnants by now secondary and restricted to inland locations away from the coast, far more than half of the islands should still be suitable for the new taxon, making it safe for the time being.

Taxonomic rationale

The proposed English name of this new taxon follows a recent trend [e.g. ( 57)] to call members of the genus Cyornis ‘jungle-flycatchers’ rather than ‘blue-flycatchers’ because molecular data (13 4) and bioacoustic considerations (57, 7 4) strongly suggest a merger of many members of the previously recognized jungle-flycatcher genus Rhinomyias with Cyornis . Given that numerous species in the resultant genus Cyornis are no longer blue but entirely brown, the name ‘blue-flycatcher’, while formerly appropriate, is no longer suitable for this genus.

Although distinguishable from other subspecies of C. omissus in terms of plumage characters (see Diagnosis), omississimus is quite similar to them in general coloration. At any rate, plumage coloration is not an ideal taxonomic indicator in Cyornis jungle-flycatchers, many of which boast a highly conserved male plumage sporting blue upperparts and reddish underparts. Other characters, such as bioacoustic and genetic ones, may be more conducive to guiding taxonomic decision-making in Cyornis .

We recently published a bioacoustic comparison on the basis of six vocal parameters among members of the greater C. rufigastra radiation, showing that the song of the newly described omississimus from Togian exhibits considerable vocal overlap with the songs of all three analyzed subspecies of C. omissus , while distinctly differing from C. rufigastra and C. kalaoensis [see figure 2 in (7 4)]. This vocal evidence along with Togian’s proximity to Sulawesi suggest a placement of omississimus as a subspecies of C. omissus .

Based on a lack of deep differentiation in both bioacoustic and genetic evidence, we propose to classify this new taxon at the subspecies level. Upon first discovery in the field, we were generally impressed by its lowland forest occurrence, which stands in contrast to the montane forest requirements of the nominate subspecies omissus from Sulawesi. This pronounced difference in habitat preference was given much weight in supporting species- level recognition of the new Togian population in a recently published field guide to the region ( 57). However, given Gwee et al.’s (7 4) newly published data, the latter treatment has ultimately proved erroneous.

Figures

Fig. S13. Holotype of Cyornis omissus omississimus (MZB.Ornit.34.483).

Fig. S2. Google Earth satellite map of Peleng and Banggai (top) and the western half of Taliabu (bottom). Peleng and Banggai are the two largest islands of the “Banggai Archipelago”. Our main collection site, an unnamed locality “above Kokolomboi [village]”, is mapped with a yellow pin. Areas above 800m elevation are circled with a red line, indicating the presence of montane vegetation. The island of Taliabu is the largest member of the “Sula Archipelago”. Our main collection locality “Waiyo dinahana” is mapped with a yellow pin. Areas above 1,050 m elevation are circled with a red line, indicating the presence of a peculiar montane stunted forest vegetation. Within the montane zone above 1,050m, areas degraded by logging activity as reflected on Google Earth satellite imagery are mapped in turquoise and areas burnt down by extensive fires in the 1980s are mapped in dark-green. Given the outdated status of some of the satellite imagery, present-day forest degradation is likely more extensive than shown.