The density of Darwin's Nothura in northern and eastern La Pampa and in parts of Mendoza Province (Argentina) is one bird per 0.4-0.8 ha. Reportedly populations experience severe declines following long droughts, but population recovery can be rapid after conditions improve (Bump and Bump 1969).
Darwin’s Nothura becomes sexually mature at an early age and reproduces in the first breeding season following hatching. The early hatched birds may breed the same season, indicated by one male at 15 weeks old with fully developed penis (Bump and Bump 1969).
One bird in captivity succumbed to "blackhead" , a form of histomoniasis that is common in poultry (Bump and Bump 1969). Bump and Bump (1969) reported a lower incidence of internal parasitism in Darwin’s Nothura than in Spotted Nothura (Nothura maculosa), perhaps because Darwin's Nothura consumes fewer insects. Of the 27 individuals of nominate darwinii that were examined for internal parasites, 10 were free of parasites; and of 27 salvadorii, 6 were parasite free. Indentified internal parasites of Darwin's Nothura included coccidia, flukes, tapeworms, roundworms and thorny-headed worms; the most frequent parasites were a gizzard worm (Habronema), a cecal worm (Subulura) and a filaroid worm (Tetracheilena). Of these only Habronema seems to seriously affect Darwin’s Nothuras, and then mostly young birds (Bump and Bump 1969).