Forpus cyanopygius insularis

Silva, Héctor Gómez de, Pérez Villafaña, Mónica G., Cruz-Nieto, Javier & Cruz-Nieto, Miguel Ángel, 2020, Are some of the birds endemic to the Tres Marías Islands (Mexico) species?, Bulletin of the British Ornithologists’ Club 140 (1), pp. 7-37 : 21-23

MEXICAN PARROTLET Forpus cyanopygius insularis (vs. F. c. cyanopygius / pallidus total score 7)

Coloration.—Males have breast, belly, neck-sides and postocular region pale malachitegreen, somewhat glaucous, contrasting strongly with the yellowish-green or apple-green cheeks, throat, forehead and forecrown vs. apple-green underparts in slight contrast (if any) with the face colour ( Figs. 11–12; Ridgway 1911, Grant 1965a, based on 21 male and 15 female insularis vs. 20 male and 31 female cyanopygius , www.inaturalist.org/observations/5258308, www.inaturalist.org/observations/5258315 [score 2]). This coloration is similar to male Pacific Parrotlet F. coelestis of western Ecuador and north-west Peru (e.g., www.hbw.com/ ibc/photo/pacific-parrotlet-forpus-coelestis/close-pacific-parrotlet and www.hbw.com/ibc/ photo/pacific-parrotlet-forpus-coelestis/male; the illustration of the later species in del Hoyo & Collar 2014 is inaccurate). Rump, lower back and greater coverts of males bright cerulean blue vs. bright turquoise-blue ( Ridgway 1911, Grant 1965a [score 1]). Secondaries and proximal primaries darker and duller blue, edged cerulean blue vs. greenish blue (nearly cerulean blue) edged distally with pale yellowish green ( Ridgway 1911 [score 2]). A. J. Grayson (in Lawrence 1872), Lawrence (1872), Ridgway (1888, 1911) and Grant (1965a) described the upperparts of both sexes of insularis as darker and more glaucous green (not scored, we are unable to discern this difference in the three insularis vs. six cyanopygius / pallidus specimens at IBUNAM). Grant (1965a) added that the flanks and undertail-coverts are the same colour as the breast / belly in all insularis males in his sample, but the detailed description of insularis by Ridgway (1911), the two IBUNAM specimens of adult male insularis , and our field photographs (e.g., Fig. 11) contradict that.

Morphometrics.—Larger in all external measurements (score 2).

Additional information.—Smith et al.’s (2012) molecular study found that insularis has diverged more from a common ancestor than cyanopygius / pallidus, consistent with a faster rate of divergence in small, isolated populations ( Woolfit 2009), and the Bayesian modelling programme BP&B assigned the probability of insularis being a separate species as higher than 95%.