Scarlet-headed Blackbird

Male scarlet-headed blackbirds average 25 cm (9.8 in) long and weigh an average of 86 g (3.0 oz). Females average 22.5 cm (8.9 in) long and weigh an average of 75 g (2.6 oz). The sexes have the same plumage. Adults have a thin black stripe behind the lores and black eyelids. The rest of their head and their neck, upper breast, and thighs are scarlet-red. The rest of their plumage is a slightly glossy black. They have a black iris, a sharp, chisel-shaped black bill, and black legs and feet. Juveniles are almost entirely brownish black with a yellowish wash on the throat and breast; they gradually acquire the adult's red.

The scarlet-headed blackbird has a disjunct distribution. Its largest range from northern Buenos Aires Province in northeastern Argentina north through Uruguay into far southern Brazil's southern and eastern Rio Grande do Sul state. Further west it extends north through northeastern Argentina and southern and central Paraguay, Brazil's Paraná and western São Paulo states, extreme eastern Bolivia, and western Mato Grosso do Sul and southwestern Mato Grosso states in Brazil. There are isolated reports in Brazil east and north of its regular range. The species' second largest range is in north-central Bolivia's Beni and Santa Cruz departments. There are also small isolated populations in northwestern Argentina. The scarlet-headed blackbird primarily inhabits marshes with extensive stands of Cyperus sedge, Typha cattail, and Thalia arrowroot. It also is found in nearby grasslands and agricultural fields. In elevation it seldom exceeds 600 m (2,000 ft).

The scarlet-headed blackbird feeds mostly on insects though there are reports of its eating small frogs. During the dry season it also feeds on the seeds of cultivated crops like maize (Zea mays) and sorghum (Sorghum bicolor). It extracts prey from plant stems with its chisel bill. In the breeding season it usually forages in pairs in their territory but in the non-breeding season forms flocks that may have 100 individuals.