The American goldfinches can be distinguished by the males having a black (rarely green) forehead, whereas the latter is (like the rest of the face) red or yellow in the European Goldfinch and its relatives. North American males are markedly polymorphic and 5 subspecies are often named; at least 2 of them seem to represent a less-progressed stage in evolution however.
Males are easily recognized by their bright yellow underparts and big white patches in the tail (outer rectrices) and on the wings (the base of the primaries). They range from having solid black from the back to the upper head including the ear-coverts to having these regions medium green; each of the back, crown and ear regions varies in darkness rather independently though as a rule the ears are not darker than the rest. In most of the range dark psaltria birds (Arkansas Goldfinch) predominate. The light birds are termed hesperophilus and are most common in the far western U.S. and northwestern Mexico