Yellow Warbler (Dendroica petechia) - HBW 15, p. 745

Taxonomy: Motacilla petechia Linnaeus, 1766, northern America = Barbados.
Taxonomy complex, and numerous races described. Has hybridized with (probably) D. caerulescens and Protonotaria citrea. Races fall into three main groups: "aestiva group" of migratory N races occupying variety of damp habitats (rubiginosa, banksi, parkesi, amnicola, aestiva, morcomi, brewsteri, sonorana, dugesi); "petechia group" of sedentary, largely mangrove-dwelling taxa (rufivertex, armouri, flavida, gundlachi, flaviceps, eoa, albicollis, chlora, solaris, bartholemica, melanoptera, ruficapilla, babad, nominate, alsiosa, rufopileata, obscura, aurifrons); and sedentary, mainly S, again mangrove-dwelling "erithachorides group" (castaneiceps, rhizophorae, phillipsi, xanthotera, aithocorys, iguanae, aequatorialis, jubaris, peruviana, aureola, oraria, bryanti, erithachorides, chrysendeta, paraguanae, cienagae). The two last-mentioned groups are often regarded as collectively forming a separate species, distinct from N group, on account of sedentary nature and restricted coastal habitat. Further, these two groups have sometimes been treated as representing two separate species, but the races of "erithachorides group" on coast of NW Venezuela have head pattern approaching that of adjoining races of "petechia group"; these anomalies do not occur near any potential zone of contact, and are generally thought to be result of independent evolution of an "erithachorides-type" head pattern within "petechia group" and vice versa. Chestnut-headed Martinique race ruficapilla, usually included in "petechia group", is more similar to members of "erithachorides group" than to "petechia group" (which surrounds it geographically); this has led several recent authors to place ruficapilla within the "erithachorides group". In recent DNA study, isolated Galapagos population (aureola) found to be genetically distinct from both Latin American and North American populations, with mean sequence divergence of 3-7% from former and 6-7% from latter; further research required. Races often intergrade, and some poorly differentiated; review perhaps needed. Distributional limits of N races not always clear; breeding ranges listed below are only approximate. Further proposed races are inedita, described from extreme NE Mexico (Matamoros, in extreme NE Tamaulipas), subsumed in aestiva; hypochlora (from Arizona), synonymized with sonorana; and cruciana, described from Virgin Is (St Croix), treated as synonym of bartholemica. Forty-three subspecies currently recognized.