The present paper describes the population parameters, the behavior, and the geographic range of Parides burchellanus (Westwood, 1872), an endangered papilionid butterfly from Brazil. Population biology was described based on a 13-mo mark-recapture program in a site of riparian forest in Minas Gerais, southeastern Brazil. The range of the population size was 10–30 individuals (with a maximum near 100 individuals). Sex ratio was male biased, with males dominating in all months. The age structure was not stable, with an increase in intermediate and old individuals before the population break in the dry season. The residence time was 23.2 ± 18.4 d for males and 16.4 ± 12.5 to females, with a maximum of 73 d recorded for males and 64 d for females. Males can travel distances of up to 950 m and females up to 650 m. When searching for P. burchellanus populations in 63 sites with suitable habitats, only seven actually had resident populations. A combination of high habitat specificity for larvae and adults could explain the rarity of this butterfly. The available data could be used in conservation programs for P. burchellanus, which should include protection of the habitats of all known colonies so far.