This is the southern component of the two species of Marshbirds. In turn, the two marshbirds are relatively closely related to the Saffron-cowled Blackbird (Xanthopsar flavus). The Brown-and-yellow Marshbird is a large, robust and pot-bellied icterid which is brown and yellow. It is a paler brown than the Yellow-rumped Marshbird (P. guirahuro) and has a brown rump. In addition, the flanks and thighs of the Brown-and-yellow Marshbird are brown. It’s range is farther south and essentially encompasses the Pampas Region, from southernmost Brazil and Uruguay through eastern Argentina to southernmost Buenos Aires and La Pampa. Brown-and-yellow Marshbirds are found in large open areas of grassland or marshland, particularly areas with dense Pampas Grass (Cortaderia sp.) stands, where this species often breeds. It will also use shrubs, and trees at edge of the grassland but does not appear to require them for habitat. This species sometimes is parasitized by the Shiny Cowbird (Molothrus bonariensis), which lays both immaculate white and spotted eggs. The marshbird rejects the white eggs but accepts the spotted eggs, suggesting it is one of the species which maintains this egg color polymorphism in the cowbird.