Phylloscopus suaramerdu, 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 : 33-37

SM5:

Phylloscopus suaramerdu , species nova

(Peleng Leaf-Warbler;

urn:lsid:zoobank.org:act:ED7A42E3-0F42-400B-8195-9E204EEFE169

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

Holotype

MZB.Ornit.34.440 ( fig. S8 ); adult male collected 20 Dec 2013 above Kokolomboi village (~ 950m) on Peleng Island (S 01⁰ 17.561 '; E 122⁰ 52.520 '). Collected by the Rheindt / LIPI field party, including tissue samples from breast muscle and liver; skin prepared by Suparno; field number Pel14; some molt; low fat; weight 8.5g; wing length 5.6cm; wing spread 15.5cm; total length 10.3cm; bill 1cm; tail 4.2cm; tarsus 2.1cm.

Description of holotype

The crown (from forehead to nape) is cold brown (2.5Y 2/2), delimited below by a narrow long white supercilium from bill base to napeside. Lores dark greyish brown (2.5Y 3/1) extending to just behind eye in the form of an eyestripe cutting through a broken white eye ring formed by small feathers peripheral to the eye. Black rictal bristles. Ear coverts and malar, facial and moustachial regions show white-and-dusky grizzling. Most of upperparts, including mantle, scapulars and rump, are mid-olive (5Y 4/4), while remiges are distinctly darker-olive (5Y 3/2) but have paler olive outer edging concolorous with mantle. Upperwing coverts have outer webs largely concolorous with mantle and inner webs concolorous with remiges. Rectrices are dark olive above (5Y 3/2) with brighter basal edging roughly concolorous with mantle, and have a more silvery sheen below (5Y 5/1). The white chin and throat are characterized by sporadic dusky speckles and lemon streaks increasing towards the lower throat, and grading into a fully lemon to sulphur yellow breast and belly (5Y 9/12). The yellow on the breast and belly has an olive-mottled appearance because of olive feather tips (5Y 4/4), especially pronounced towards the flanks, and white feather bases, especially pronounced towards the abdomen. The vent is solid lemon-yellow (5Y8/7). Iris dark-brown; bill black. Tarsus, toes and claws pinkish-grey with toepads paler yellowish.

Diagnosis

A small Phylloscopus leaf-warbler typical of the P. poliocephalus leaf-warbler radiation from across Australo-Papua and Wallacea. Notable for its lack of both a central crown stripe and wingbars, and its lemon-yellow underparts contrasting with a white throat. As is typical for this cryptic genus, bioacoustic distinctions between this species and its neighbors are pronounced and possibly more important than morphological differences. Nevertheless, the new species differs strikingly from all other Wallacean members of the P. poliocephalus species complex in a number of plumage features.

P. suaramerdu is distinguished from all other Phylloscopus residents of the Sulawesi sub-region (including P. sarasinorum , P. nesophilus and the new species from Taliabu described below) by its white (not yellowish) supercilium and throat, and by its grey-and- white mottled sides of face (versus yellow-and-grey or unmottled appearance). It differs additionally from P. sarasinorum in the lack of a pale central crown stripe, more olive- mottled breast, and lack of white in tail. It differs additionally from P. nesophilus in its greater contrast between crown and mantle color, and – in particular from the geographically proximate eastern and south-eastern Sulawesi populations – in its paler yellow lower underparts. For differences from the new species from Taliabu, see below in SM6.

P. suaramerdu generally differs from remaining members of the P. poliocephalus complex in the combination of dusky-and-white facial grizzling and a paler yellow, mottled breast. Specifically, the new species differs additionally from P. poliocephalus giulianettii (Central Papua) and P. ceramensis (Seram) in its lack of wingbars and lack of a central crown stripe; from P. p. poliocephalus (West Papua), P. waterstradti (Obi, Bacan) and P. everetti (Buru) in its lack of wingbars and browner (versus greyish) crown; from P. floris (Flores) in its white (versus intensely yellow) throat and less bright olive upperparts; and from P. presbytes (Timor) in the lack of a central crown stripe.

Etymology

The new species name is derived from “suara merdu” in Bahasa Indonesia, translating as “melodious voice”, referring to the pleasing vocalizations of this bird that FER heard hours before the first individual was seen, allowing for predictions prior to visual confirmation that this would be a new Phylloscopus leaf-warbler to science. The expression is treated as a noun in apposition.

Individual, sex and age-related variation within the taxon

Only one adult male (the holotype) is available, but observations and photos of additional adult specimens suggest limited intra-specific variation.

History of discovery

During a visit to the highlands of Peleng between 23-30 March 2009, FER and Filip Verbelen frequently encountered this species at elevations between 700-900m ( 49). When hiking up to these elevations for the first time and hearing the melodious warble of this taxon in the distance, its superficial vocal resemblance to other members of the Wallacean Phylloscopus radiation prompted FER to predict that this would be a new leaf-warbler taxon long before they laid their eyes on it. Once they first saw it, it was noticeable for its unusual behavior of frequently climbing along larger branches and trunks of trees in the manner of a treecreeper ( Certhia ). On our collecting expedition to Peleng between 18-23 Dec 2013, the species was less commonly encountered ( 19), probably because of seasonality.

Distribution and status

This new leaf-warbler is restricted to the highland forests of western Peleng in the Banggai Archipelago at elevations above 700m, reaching the highest island altitude above 1000m ( fig. S2 ). Its presence on other islands in the Banggai Archipelago must be in serious doubt because only one of them, the small island of Bangkulu, slightly exceeds 600m in elevation, of which only 5 ha of land lie above 600m, still well below the lowest known elevational occurrence of the new species. Beyond the Banggai Archipelago, P. suaramerdu is replaced by Sulawesi Leaf-Warbler P. nesophilus on the adjacent peninsula of Sulawesi to the west as well as by another new species (see below) on the Sula Archipelago to the east.

The conservation situation of P. suaramerdu must be equally dire as that of the new Peleng Fantail Rhipidura habibiei , with a natural extent of occurrence not much larger than 25,000 ha ( fig. S2 ), of which at least ~40% appears to have been seriously degraded or destroyed by now. For more detailed information, see SM2.

For a detailed taxonomic rationale, see SM6.

Figures

Fig. S8. Holotypes of Phylloscopus suaramerdu (MZB.Ornit.34.440) (top), and Phylloscopus emilsalimi (MZB.Ornit.34.352) (bottom).

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.