Chlorospingus semifuscus xanthothorax

Sánchez-Nivicela, Manuel, Avendaño, Jorge Enrique, Sánchez-Nivicela, Juan C., Torres, Ana, Fuchs, Jérôme, Bird, Bentley & Bonaccorso, Elisa, 2021, A taxonomic assessment of Chlorospingus flavopectus phaeocephalus and Chlorospingus semifuscus (Passeriformes: Passerellidae), including the description of a new subspecies, Zootaxa 5057 (2), pp. 151-180 : 166-167

Chlorospingus semifuscus xanthothorax (subspecies nova)

Diagnosis.—Similar to C. f. phaeocephalus ( Fig. 1 ) but inhabits the cloud forest of the southwestern Andes of Ecuador. The type series is presented in Figure 7 . The color of the pectoral band of C. f. phaeocephalus is somewhat more yellowish than in C. s. xanthothorax, as supported by Zimmer´s (1947) review. The pectoral band in C. s. xanthothorax is a rather bright combination between spectrum yellow (C.55) and olive-yellow (C.52), with more olive yellow on flanks, whereas the pectoral band in C. f. phaeocephalus is a brighter lemon chrome (b. 21) on the center with more olive-yellow (C.52), mainly on the flanks. Both C. s. xanthothorax and C. f. phaeocephalus present pale silvery yellow iris. In examined specimens, the relevant plumage difference between adult individuals in these two populations might be the throat pattern coloration. In C. f. phaeocephalus, the throat is more buff-white or whitish with some grayish or glaucous speckles (see holotype description below), but this feature is age variable and difficult to distinguish in the field given the poor light conditions of cloud forests. In both taxa, postocular spots on adults are related to ontogeny and probably sex (females). Both sexes of C. s. xanthothorax are smaller than the other members of C. f. phaeocephalus and the C. semifuscus group ( Fig. 5 ).

Description of Holotype MECN 9592 (in life).—Adult. Weight 22 g. Culmen, lores, fore crown, supercilium and lower auricular region blackish neutral gray (C.82) with weak hints of yellowish olive-green (C.50) randomly distributed on some barbules. Crown and back of the head are dark neutral gray (C.83). Nape, back, rump, wing-coverts, and upper tail coverts are yellowish olive-green (C.50). On upper-wings, primaries, secondaries, tertials inner webs, and under wings are brownish olive (C.29), better diagnosed when wings are folded, mainly at the end of the primary projection. Bill: upper mandible, matte black, with some hints of pale russet vinaceous (C.221D) near the gape. Lower mandible is a mixture of matte black with some light russet vinaceous (C.221D). The malar transitions from a very pale cream color (C.54) near the base of the bill reaching the throat to a light neutral gray (C.85) with some hints of yellowish olive-green (C.50) barbules. It presents a thin blackish neutral gray (C.82) moustachial stripe. Chin is buffy-white. Throat center presents the same transition between pale cream color and dark neutral gray. In the field, the throat plumage can be perceived as a mixture of speckled dark gray and buff. The pectoral band is a fairly bright combination between spectrum yellow (C.55) and olive-yellow (C.52), with more olive-yellow (C.52) on flanks. Center of belly is a pale pearl gray (C.81) and/or silvery-white that narrows in the vent. Flanks are bright spectrum yellow (C.55) with some pale neutral gray (C.86) on middle flanks. Tail from above is yellowish olive-green (C.50). Outer webs spectrum yellow and inner webs are dull yellowish olive-green (C.50), with black rachises. Tail from below dull yellowish olive-green (C.50). Under-tail coverts are spectrum yellow (C.55). Iris: silvery yellow. The iris can vary, and is perceived as pale-yellow in the field. Tarsometatarsus, flesh color (C.5). Tarsi and toes light neutral gray with hints of flesh color. Specimen measurements MECN 9592 ( Fig. 7 ); wing chord mean 86.7 mm, tarsus mean 22.3 mm, tail 56.0 mm, bill length from the distal edge of the nostril to the tip of the bill 8.5 mm, bill depth at the center of nostrils 5.4 mm and bill width at center of nostrils 4.5 mm. Empty stomach. Showing molt at both P10 (primaries). Type locality: Sambotambo road (boundaries of Buenaventura Reserve; 03° 39’ 07.32” S, 79° 44’ 36.32” W; 969 m elevation; Fig. 1 ), El Oro Province, Ecuador; collected on 8 September 2017, by MSN and JSN; prepared by Hernando Román; field catalog number EOC 002; GenBank accession number provided in Appendix I.

Paratypes.— Two female specimens complete the type series ( Fig. 7 ), as follows. Study skin MECN 9214 ; wing chord mean 64.00 mm, tarsus mean 28.72 mm, tail 60.00 mm, bill length from the distal edge of the nostril to the tip of the bill 8.10 mm, bill depth at the center of nostrils 5.32 mm and bill width at center of nostrils 4.83 mm. Locality: Buenaventura Reserve at 1090 m; collected on 2 January 2017, by MSN and JSN. MECN 9593 ; wing chord mean 65.00 mm, tarsus mean 27.70 mm, tail 52.00 mm, bill length from the distal edge of the nostril to the tip of the bill 8.18 mm, bill depth at the center of nostrils 5.14 mm and bill width at center of nostrils 4.79 mm; collection site is the same as holotype. Both skins prepared by Hernando Román; field catalog numbers EOC 001 and EOC 003, GenBank Accession numbers provided in Appendix I .

Dawn song.—Two complete dawn songs of this taxon by MECN 9592 (XC607786, XC607789) are deposited at xeno-canto.org. For description per element see Table 3 ; for spectrograms, see Figure 6 , and Supplementary Material A2. A single, sharp, high-pitched element (note “a”) repeated several times before pre-trill notes and dry staccato trill similar than C. s. semifuscus ; but pre-trill notes “b” and “c” delivered in different order and post-trill notes different than nominal.

Etymology.—We choose an epithet that matches the obvious field diagnostic feature of this new member of the C. semifuscus group, which is its olive-yellow breast band. Xanthothorax combines two Greek words, xanthos meaning yellow and thorax meaning breast ( Jobling 2010).

Distribution and habitat.—Mainly found in the borders of humid subtropical lower montane cloud forests in El Oro Province and in similar ecosystems in adjacent Loja Province ( Ridgely & Greenfield 2001). To our knowledge, this subspecies is restricted in its northern limit by the arid Jubones River valley. The southernmost record is from Vicentino south of Puyango River, in Loja Province ( Best et al. 1993). Its southern distribution might be limited by the transition from the Chocoan humid to Tumbesian dry ecosystems, between Puyango and Catamayo rivers. Its elevation range is ~ 800‒1700 m. Uncommon and localized, in general, but frequently found in Buenaventura Reserve ( Robbins & Ridgely 1990) and in suitable habitat and elevation in El Oro province ( Garzón-Santomaro et al. 2019) and adjacent Loja province.

Breeding.—Juveniles were reported begging for food on 26 February (vocalization recorded by MSN, XC 607791) and 9 September 2017. Both breeding records were within the area where we collected the holotype .

Figures

FIGURE 1. Distribution and plumage of populations of the Chlorospingus semifuscus group in the northwestern Andes down to Angamarca river, and Chlorospingus flavopectus phaeocephalus in the eastern Andes of Colombia and Ecuador with the putative southwestern populations in Ecuador. The map includes records (circles), geographic barriers (rivers, and Cajanuma Transversal Ridge), and the two sites with no records of the western populations (red crosses). Bird artwork by Carmen Lu Páez.

FIGURE 5. A. Wing length (mm). Males (m) and females (f). From left to right: C. f. phaeocephalus (CFP) only two females, C. s. livingstoni (CSL), C. s. semifuscus (CSS), C. “Chimborazo” (CCH) (only males), and C. “El Oro”. B. Bill depth from nares (mm). Males (m) and females (f). From left to right: C. f. phaeocephalus (CFP) *only two females, C. s. livingstoni (CSL), C. s. semifuscus (CSS), C. “Chimborazo” (CCH) **only males, and C. “El Oro” (CEO).

FIGURE 6. Structural differences in dawn song elements. Between C. s. semifuscus, “a” notes, pre-trill notes (“b” and “c”), trill, and posttrill notes (“d” and “e”), C. “El Oro”, the order of “c” + “b” notes in C. “El Oro” follow our comparisons with C. s. semifuscus (see Table 3 for descriptions per note) and C. f.phaeocephalus, notes “a” + “a1”, notes “b”, trill and notes “c”. Bird artwork by Carmen Lu Páez.

FIGURE 7. Chlorospingus semifuscus xanthothorax.Holotype, male in center (MECN-9592) and two female paratypes MECN- 9593 (left) and MECN-9214 (right).