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 Òzone of intergradationÓ 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 Choc— 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

Ò

Concolor with back or tinged bronzy, sometimes strongly

Contrasting, brilliant green forecrown or ÒfrontletÓ; rest of crown like back

Central rectrices

Ò

Bronze-green to dull dark green, tip tinged bluish in some

Concolor with back or slightly more bluish, especially distally

Lateral rectrices

Ò

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

Ò

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

Ò

Patch of brilliant purple, passing to bright dark blue laterally

Purple patch smaller, more violet, also passing laterally to dark blue

Lower throat

Ò

Broad white diagonal band on each side interrupted medially by green

White band continuous across throat, broadest medially: chevron-shaped

Side of head

Ò

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

Ò

Uniform pale green

Uniform darker green

Posterior underparts

Ò

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

Ò

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

Ò

Diagonal band like _, green medially

Diagonal band confluent with white of throat

Sides of neck

Ò

Purple patch smaller, passing laterally to bright greenish blue

Similar but laterally darker blue

Breast and abdomen

Ò

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 Òwashed-outÓ; 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 Ð 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: GeoffroyÕs 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. CortŽs-Herrera, T. Ellery & P. Salaman. 2015. Revision of the status of Bird species occurring in Colombia, with discussion of BirdLife InternationalÕs new taxonomy. Conservaci—n Colombiana 23:3-48.

 

__________________________________________________________

 

Comments from Zimmer: ÒYES.  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.Ó

 

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

 

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