Vireo, Vieillot, 1808

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 : 23

GOLDEN VIREO Vireo hypochryseus sordidus (vs. V. h. hypochryseus total score 5–6)

Coloration.—Throat, breast, flanks and upperparts duller and greener in sordidus, especially in fresh plumage and when specimens collected in the same season are compared (score 1 or possibly 2, Grant 1965a, based on 30 male and 23 female sordidus vs. 44 male and 20 female hypochryseus ). Grant (1965a) reported that Nelson’s (1898) claimed difference in bill colour is incorrect.

Morphometrics.—Larger in all external measurements, especially tail length of both sexes and wing length of females (score 2), with a significantly shorter coracoid both absolutely and relatively (effect size almost reaches the threshold for score of 3, but we assign a score of 2) and a relatively shorter femur (not significantly different between taxa, whereas all external measurements are larger [not scored]). Arbeláez-Cortés et al. (2014) analysed the morphometrics of ten sordidus and 37 specimens from the rest of the range, and confirmed the larger size of sordidus.

Additional information.— Arbeláez-Cortés et al. (2014) and Ortiz-Ramírez et al. (2018) reported reciprocal monophyly but shallow genetic divergence between these taxa.