The nominate subspecies of the Blue-fronted Amazon, Amazona aestiva aestiva, (above) has a red "shoulder"
and leading edge to its wing.
The nominate subspecies of Blue-fronted Amazon comes from eastern Brazil.
Shown above is the subspecies Amazona aestiva xanthopteryx, also called the Yellow-winged Amazon, which has a yellow "shoulder" and leading edge (but, unlike the "Yellow-shouldered Amazon", has a blue brow). The Yellow-winged Blue-fronted also generally has more yellow on its face than its red-shouldered cousin.
The Yellow-winged Blue-fronted Amazon comes from Bolivia, eastern Brazil, Paraguay and northern Argentina.
Some Blue-fronted Amazons have an entirely blue face without yellow on the head, particularly those from north-western Argentina.