Yellow-headed Amazon - Taxonomy

Taxonomy

This species is part of the Amazona ochrocephala complex, which also includes the Yellow-naped Amazon (A. auropalliata). This complex, "a taxonomic headache", is considered a single species by some authorities and split into three species by others. The split is mainly based on the amount of yellow in the plumage, the color of the legs and bill, the proximity of A. oratrix and A. auropalliata in Oaxaca, Mexico, without apparent interbreeding, and the presence of both A. ochrocephala and A. auropalliata in northern Honduras. This evaluation has, however, been confused by misunderstandings regarding the plumage variations in the populations in northern Honduras, where birds vary greatly in amount of yellow on the head, crown and nape, but have pale bills and a juvenile plumage matching A. oratrix, but neither A. ochrocephala nor A. auropalliata. In 1997, the population from the Sula Valley in northern Honduras was described as a new subspecies, hondurensis, of A. oratrix. A. auropalliata caribaea on the Islas de la Bahía, which is relatively close to the recently described A. oratrix hondurensis, may have a relatively pale lower mandible, indicating that gene flow may occur between the two. If confirmed, this could suggest that the two are better considered conspecific. Alternatively, it has been suggested that caribaea and parvipes, both typically considered subspecies of A. auropalliata, may be closer to A. oratrix than they are to the nominate A. auropalliata. Both are relatively small and have red on the shoulder like A. oratrix, but unlike nominate A. auropalliata. The members of this complex are known to hybridize in captivity, and recent phylogenetic analysis of DNA did not support the split into the three "traditional" biological species, but did reveal three clades, which potentially could be split into three phylogenetic species: a Mexican and Central American species (including panamensis, which extends slightly into South America), a species of northern South America, and a species from the southern Amazon Basin. The Central American clade can potentially be split further, with panamensis (Panama Amazon) and tresmariae (Tres Marías Amazon) recognized as two monotypic species.

According to the traditional split, A. oratrix includes the taxa tresmariae (from Tres Marías Islands), belizensis (from Belize) and hondurensis (from Sula Valley, Honduras) as subspecies. An additional subspecies, magna, has sometimes been recognized for the population on the Gulf slope of Mexico, but today most authorities consider it invalid, instead including this population in oratrix, which also occurs on the Pacific slope of Mexico. In contrast, the population in north-western Honduras and adjacent eastern Guatemala (near Puerto Barrios), which resembles A. oratrix belizensis and commonly is included in that subspecies, may represent an undescribed subspecies. It has sometimes been referred to as guatemalensis, but until this population is officially described, the name remains provisional.

The origin of the common epithet "Double Yellow-headed" is that this species is differentiated from the others in the Yellow-headed Amazon complex by possessing both the yellow nape and yellow crown of its two close relatives, hence a "double-yellow" head.