Proposal (774) to South American Classification Committee

Split Schistes geoffroyi into two species

This split was recently advocated by del Hoyo & Collar (2014) and somewhat amplified by Donegan et al. (2015). The taxa involved are nominate S. geoffroyi, which occurs in the Eastern Andes of Colombia and predominantly on the eastern slope of the Andes southward to Bolivia, and S. g. albogularis of the Western Andes and the western slope of the Central Andes of Colombia, south on the Pacific slope to SW Ecuador. Historically, these had been considered separate species by almost all authors until they were lumped without explanation by Peters (sound familiar?). Although Schuchmann (1999) mentions a “zone of intergradation” in W Ecuador, Ridgely & Greenfield (2001) intimate that there is a large gap between the known distribution of albogularis and extreme SW Ecuador, where perhaps the nominate race occurs, and they suggest that two species may be involved. Although sharing a similar altitudinal range, the preferred habitat of albogularis is much more humid and appears to represent a typical Chocó distribution. Del Hoyo & Collar base their recommendation for the split entirely upon differences in plumage color, but Donegan et al. added information on vocalizations.

The following table gives the details of their plumage evaluations, amplified and amended by my examination of series of specimens of both in the ICN collection.

Character	Sex	geoffroyi	albogularis
Upperparts	♂	Green to bronze-green, passing to bright bronzy to coppery-bronze on rump and upper tail coverts	Uniform dark green (more emerald-green); at most slightly more bronze-green on lower back
Crown	“	Concolor with back or tinged bronzy, sometimes strongly	Contrasting, brilliant green forecrown or “frontlet”; rest of crown like back
Central rectrices	“	Bronze-green to dull dark green, tip tinged bluish in some	Concolor with back or slightly more bluish, especially distally
Lateral rectrices	“	Green with broad subterminal band dark blue; tips broadly fringed white (1-2 mm)	Similar but white fringe narrower (< 1 mm), grayish white
Throat and chin	“	Bright green, the feathers with grayish-white bases and fringes giving densely spotted pattern	Brilliant green, the feathers with extensive white bases giving spotted effect, lateral feathers often mostly white
Side of neck	“	Patch of brilliant purple, passing to bright dark blue laterally	Purple patch smaller, more violet, also passing laterally to dark blue
Lower throat	“	Broad white diagonal band on each side interrupted medially by green	White band continuous across throat, broadest medially: chevron-shaped
Side of head	“	Small white postocular spot, prolonged posteriorly into a narrow stripe in some	Small white postocular spot, often lacking and never prolonged into a stripe
Breast	“	Uniform pale green	Uniform darker green
Posterior underparts	“	Green feathers with pale grayish fringes that become broader on abdomen, especially medially giving blotchy effect	Green feathers continue posteriorly, on lower medial abdomen with inconspicuous dark gray fringes
Under tail coverts	“	Green with broad pale gray bases and fringes	Green with narrower, paler grayish fringes
Throat	♀	Pale green with broader grayish-white fringes, looks more densely spotted	Entirely immaculate white
Lower throat	“	Diagonal band like ♂, green medially	Diagonal band confluent with white of throat
Sides of neck	“	Purple patch smaller, passing laterally to bright greenish blue	Similar but laterally darker blue
Breast and abdomen	“	Grayish white fringes more obvious, especially posteriorly, center of lower abdomen often plain grayish white	Feathers of medial lower breast and abdomen green with inconspicuous dark gray fringes , medial abdomen grayish-white

Donegan et al. also documented vocal differences with multiple sonograms, pursuing a difference in song between males of the two taxa first noticed by Ridgely & Greenfield: more rapid and less varied in geoffroyi, slower and more lilting and varied in albogularis.

A striking feature, not noted by either del Hoyo & Collar or Donegan et al. and also not correctly illustrated in Schuchmann (1999), is the rather conspicuous difference in the green body color between the two taxa, obvious in good light even from several meters away: the green of geoffroyi, especially on the breast, looks pale and “washed-out”; that of albogularis is very much darker, which greatly enhances the contrast with the white of the throat and with the frontlet. A second feature not noticed by these authors is that sex for sex, albogularis is appreciably larger in most dimensions, especially bill length and wing length – but actually has a shorter tail. The differences in wing length in particular are very highly significant (p<0.001 in males, p<0.01 in females), in bill length highly significant (p<0.01) in males, and the wing of albogularis is not only longer but also significantly narrower (p<0,01)in both sexes. The difference in tail length (in the opposite direction) is significant (p<0.01) only in females (see table below).

Measurements of S. g. geoffroyi and S. g. albogularis, with p values from t-tests

Parameter	S. g. geoffroyi ♂♂ (n=7)	S. g. albogularis ♂♂ (n=10)	p	S. g. geoffroyi ♀♀ (n=6)	S. g. albogularis ♀♀ (n=5)	P
Body mass	3.67±0.29	3,71±0.21	0.81	3.25±0.17	3.42±0.10	0,18
Total culmen	15.00±0.76	16.43±0.75	0.0016	15.88±0.96	17.18±0.99	0.055
Folded wing chord	51.46±1.10	55.38±1.23	<<0.001	47.02±1.61	50.72±0.95	0.0014
Extended wing length	57.36±1.41	60.20±0,99	0.0002	51.98±1.99	55.38±0.85	0.0056
Tail length	33.61±0.82	32.69±0.96	0.096	31.27±0.78	28.84±1.39	0.0053
Wing form (L/W)	2.998±0.099	3.259±0.076	<<0.001	2.930±0.111	3.223±0.075	0.0006

Specimen photos:

In terms of distribution, albogularis is restricted to the Western Andes in Colombia and is found, at least locally, on both slopes; geoffroyi occurs on both slopes of the Eastern and Central Andes. Thus, the two forms are isolated by the middle and upper Cauca River valley, with its hot, dry climate; the distance between the ranges of the two is thus quite narrow, especially in the middle Cauca valley, where the two ranges are easily within sight of one another. This narrow divide also separates two related species of Scytalopus (stilesi and alvarezlopezi), among others; it comes as close to parapatry as the middle-to-upper elevation habitats of the two permit.

Within S. geoffroyi a southern subspecies, S. g. chapmani, differs in that the white 'half-collar' is reduced or lacking in southern Peru (Schulenberg et al. 2009) and apparently lacking in Bolivia, suggesting intergradation; in any case, it differs much less from the nominate than does albogularis.

Taken together, I find that the differences between these two taxa are actually greater in several respects than had been adduced by previous authors and are comparable to or greater than those between the green species of Colibri, the sister genus of Schistes. Hence, I recommend a YES on this split. I also agree that the English names proposed by Donegan et al. could be adopted: Geoffroy’s Wedgebill and White-throated Wedgebill for geoffroyi and albogularis, respectively.

F. Gary Stiles

References

Del Hoyo, J. & N.J. Collar. 2014. Illustrated checklist of Birds of the world, vol. 1 (non-Passerines). Lynx Edicions, Barcelona, Spain and BirdLife International, Cambridge, UK.

Donegan, T., A. Quevedo, J.C. Verhelst, O. Cortés-Herrera, T. Ellery & P. Salaman. 2015. Revision of the status of Bird species occurring in Colombia, with discussion of BirdLife International’s new taxonomy. Conservación Colombiana 23:3-48.

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Comments from Zimmer: “YES. Given the number of consistent morphological differences between geoffroyi and albogularis, and given that the two were historically treated as separate species until lumped without justification by Peters, I would say that the burden of proof falls on those who would maintain them as a single species. As Gary notes, using the sister genus Colibri as a yardstick for interspecific morphological differences, the two Schistes show at least a comparable or greater degree of morphological differentiation than the various green Colibri species.”

Comments from Jaramillo: “YES. This seems clear cut, particularly since these were separate species lumped without any clear reasoning by Peters.”

Comments from Robbins: “YES, for elevating albogularis to species status, as the morphological characters, especially dorsally are dramatic.”

Comments from Pacheco: “YES. A very convincing and illustrated proposition.”

Comments from Areta: “YES. The marked morphological differences, lack of evidence of any interbreeding and differences in vocalizations support the recognition of Schistes albogularis as a species.”

Comments from Remsen: “YES. These two seem to differ about as much or more from each other as do the two taxa of Heliothryx treated traditionally as separate species (and in the same subfamily as Schistes), so strictly from a comparative standpoint, I see no reason why these two were lumped by Peters. Vocal differences detected by Ridgely and documented by Donegan seal the deal for me.

“Gary did not mention English names. HBW used “Western Wedge-billed Hummingbird” and “Eastern Wedge-billed Hummingbird, which are accurate, but dull as dirt and cumbersome. Donegan et al. (2015) put in a plug for names they said were used by Gould, i.e. “White-throated Wedgebill” and “Geoffroy’s Wedgebill.” I like those much better, although “Wedgebill” is already in use for Australian species in genus Psophodes. Also, I don’t think Schistes uses its bill as a wedge per se --- more like knife. Knifebills? Daggerbills? Regardless, we need a separate proposal on English names.”

Comments from Stotz: “YES. On the English name question, I would go with the Geoffroy’s and White-throated Wedgebill.””