They live in grasslands, savanna, dry woodland and open forests of Brazil, Bolivia, Argentina, Paraguay and Uruguay.

[5][6] However, the fossil record of the seriemas themselves is poor, with two prehistoric species, Chunga incerta[7] and Miocariama patagonica (formerly Noriegavis santacrucensis),[8][9] both from the Miocene of Argentina, having been described to date.

Some of the fossils from the Eocene fauna of the Messel pit (i.e. Salimia and Idiornis) have also been suggested to be seriemas,[10] as has the massive predatory Paracrax from the Oligocene of North America,[9] though their status remains uncertain.

They feed on insects, snakes, lizards, frogs, young birds, and rodents, with small amounts of plant food (including maize and beans).

When seriemas catch small reptiles, they beat the prey on the ground (Redford and Peters 1986) or throw it at a hard surface to break resistance and also the bones.

[citation needed] Because of these feeding behaviors, seriemas are important by eating detritivores and helping the soil get more nutrients from dead plant matter.

[clarification needed] In contact with humans, seriemas are suspicious and if they feel threatened, usually spread their wings and face the threat.

[11] Seriemas build a large bulky stick nest, lined with leaves and dung, which is placed in a tree 1–5 m (3.3–16.4 ft) off the ground.