Most authorities seem to agree that this species should be split into 3 or 4 separate species but somebody needs to revise the taxonomy properly before such a split can take place. There are five main groups of sub-species: the griseicapillus group in Amazonia and the chaco; the aequatorialis group on the Pacific coast of South America; the griseus group in Central America and adjacent South America; the reiseri group of north-east Brazil; and the sylviellus group of eastern and south-eastern South America.