Phyllergates cucullatus sulanus, 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 : 48-51

SM7:

Phyllergates cucullatus sulanus , subspecies nova

(Sula Mountain Leaftoiler;

urn:lsid:zoobank.org:act:539857EC-044B-4C37-997F-43031FB8BCD2

) Frank E. Rheindt, Dewi M. Prawiradilaga, Hidayat Ashari, Suparno, Nathaniel S. R. Ng

Holotype

MZB.Ornit.34.394 ( fig. S12 ); adult male collected 11 Dec 2013 at Waiyo dinahana Camp (~ 1200m) above the village of Wahe on Taliabu Island (S 01⁰ 47.614 '; E 124⁰ 48.216 '). Collected by the Rheindt / LIPI field party, including tissue samples from breast muscle and liver; skin prepared by Suparno; field number Tbu62; no molt (all fresh feathers); high fat; weight 8g; wing length 5cm; wing spread 13.8cm; total length 11cm; bill 1.63cm; tail 4.7cm; tarsus 2.2cm.

Description of holotype

Crown bright rufous (7.5YR 6/10) from nape to forehead, including single rows of feathers below the eye. Posterior auriculars are mid-brown (7.5YR 3.5/3) grading into a pale orange- rufescent (7.5YR 7/6) frontwards towards the malar and moustachial regions. Mantle and scapulars to uppertail coverts are bronzy olive (2.5Y 3/4), the remiges and rectrices slightly darker and with more coppery edging (10YR 4/6). Dull white on breast reaches to chin, with an orange-rufescent tinge (7.5YR 7/6) surrounding the breast laterally and ventrally. Yellow belly and vent (5Y 8/10), brighter centrally than laterally, with a rufescent-orange suffusion to flanks (7.5YR 7/6). Underwing concolorous with central belly on axillaries, with increasingly white suffusion towards the remainder of the underwing. Dark-horn mandible. Yellow-orange tarsus on live bird. The iris color was not clearly discernible on live type specimen.

Diagnosis

One of the phenotypically most distinct subspecies of the Mountain Tailorbird or Mountain Leaftoiler Phyllergates cucullatus . Uniquely among all subspecies, the new taxon has a rufescent suffusion on throat and breast, becoming especially pronounced on breast sides and auriculars (from where it grades into the rufous crown), rendering the bird’s anterior aspect much warmer-tinged than all other subspecies. The upperparts, especially upper wings, are also warmer bronzy and the flanks tinged more rufescent than all other subspecies, making this the most reddish-looking taxon in P. cucullatus . It additionally differs from most other subspecies (except those from Sulawesi and Peleng) in the rufous crown’s more posterior extension to the nape and in the absence of a pale supercilium.

It further differs from cucullatus (Java, Bali, Sumatra), cinereicollis (Borneo), malayanus (Malay Peninsula) and all subspecies further to the north and west in the absence of a strong grey hindcollar band and/or strongly grey breast sides. In many aspects, the new taxon is similar to the set of subspecies on Sulawesi (riedeli, stentor, meisei, hedymeles), but dramatically differs in its much more extensive yellow on belly and lower breast (versus yellow on the flanks only, or a light-yellow suffusion on the lowermost underparts, or a near- complete absence of yellow, respectively). For additional differences from the new subspecies on Peleng, see SM8.

Etymology

We name this taxon after the Sula Archipelago which it inhabits, sulanus being adjectival.

Individual, sex and age-related variation within the taxon

The juvenile and immature plumages remain undocumented. Among the five adult specimens (three males and two females) procured, there is minor variation in the intensity of the orange-rufous crown color (being especially more orange in one male, 34.394), the intensity of the rufescent flank wash, the ventral extent of the white breast, and the intensity of the rufescent suffusion on throat and breast.

History of discovery

Davidson et al. ( 64) reported the first observations of a Phyllergates leaftoiler (then called an Orthotomus tailorbird) for Taliabu, and characterized the population as inhabiting montane forest above 500m and possibly in need of taxonomic description. FER found this population commonly in disturbed montane forest to over 1,100 m, with a few records in dense secondary bamboo thickets down to 50m ( 48), and our collecting expedition re-encountered this form abundantly at elevations around 1,300m ( 19).

Distribution and status

To the best of our knowledge, this new subspecies is currently only known from Taliabu in the Sula Archipelago. There, it inhabits disturbed situations (forest edge, bamboo thickets) mostly in the mountains, with the highest record at 1300m, but presumably ranging to the highest point at over 1400m ( 19, 48, 64). On other islands, mountain leaftoilers rarely range lower than ~500m ( 57), but Rheindt ( 48) exceptionally recorded the new taxon on Taliabu from an extensive bamboo thicket at ~50m, demonstrating that this population may tolerate lower elevations. The presence of this leaftoiler on the other two main Sula islands, Mangole and Sanana, is likely, especially on the former, which rises to over 1,100m, but perhaps also on the latter, which reaches to a little over 600m. However, it has probably been overlooked owing to a lack of fieldwork at higher elevations on these two islands. On the Banggai Archipelago, the species is represented by another novel subspecies (see below) that replaces sulanus there. Its predilection for disturbed forest situations and wide elevational tolerance as compared to other insular mountain birds probably means that it is currently not of conservation concern.

For a taxonomic rationale, see SM8.

Figures

Fig. S12. Holotypes of Phyllergates cucullatus sulanus (MZB.Ornit.34.394) (top) and Phyllergates cucullatus relictus (MZB.Ornit.34.442) (bottom), respectively.