It prefers open landscapes with a simple structure and low vegetation, such as pampas, campo cerrado and open chaco woodland, but is also found in cultivated fields (Canevari et al. 1991, Folch 1992, Sick 1993, Parker et al. 1996, García-Eriza and Gómez-Villafañe 2016). Population densities in grassland are several times that in agricultural areas, and birds were found to occupy 51% of a grassland area, but less than 5% of an agricultural locality (Giordano et al. 2008). It breeds in areas with dense vegetation cover of tall grasses (García-Eriza and Gómez-Villafañe 2016, G. J. Fernández in litt. 2020). Eggs are laid on the ground in an area of trampled grass; the male incubates the eggs alone and raises the young (Kirwan et al. 2021). Food items include insects and grasses (Kirwan et al. 2021).

Rhea americana has a large range in eastern and southern South America, ranging from northeast Brazil, east and northeast Bolivia, Paraguay, Uruguay to north-east and east Argentina south to the Río Negro (Folch 1992, Kirwan et al. 2021). It has declined markedly and the healthiest populations are now believed to be in parts of the Chaco region (Folch 1992).

Conservation Actions Underway
CITES Appendix II. Captive-bred individuals are being reintroduced in parts of their native range (Vera-Cortez et al. 2018). 

Conservation Actions Proposed
Survey to quantify the population size. Research threats to the species and quantify the impact of habitat conversion and degradation on the population size. Monitor the population trend. Monitor levels of illegal domestic and international trade.
Preserve remaining natural habitat (Giordano et al. 2010). Include pastures and grasslands in agricultural ecosystems (Bellis et al. 2004). Consider managing grassland areas to keep them free of shrubs. Establish dispersal corridors to connect fragmented patches of open grassland (García-Eriza and Gómez-Villafañe 2016, Pedrana et al. 2018). Effectively enforce restrictions on hunting and trade (Bellis et al. 2004).