In the presente study on the mating of Nothura maculosa (Temminck, 1815) the tertiary and quaternary sex ratios were joined together The sex ratio was 1:1 or when deviated, favouring females When such deviations occur, they are probably due to quaternary sex ratio The inversion of sexual rôles could be responsible for the larger number of females, since males are more exposed to mortality risks The mating system in the Tinamidae is simultaneous poliginy for the male and sequential poliandry for the female, Emlen & Oring, 1977 Such complexity in the mating system results in a greater share among all individuals in the reproduction effort in relation to poliginy The sexual inativity of males for at least around 24 days after the begining of incubation, allows new males to participate in the reproductive effort The assumption that some of the females wuld be excluded from the reproductive effort when sex ratio is deviated in their favour, probably can not be held as true Bump & Bump, 1969, reported that 95% of the eggs examined (114 eggs), were fertile There are reasons to believe that neariy all females will successfully copulate under these circunstances