We studied the population biology and natural history of the endangered Swallowtail butterfly, Euryades corethrus to establish parameters for its conservation. We used capture-mark-recapture techniques and observations to study demography, mobility, foraging strategies, and sexual behavior. We captured 588 males and 367 females. Daily captures varied from zero to 44 per sex; sex ratio was male-biased. Abundance estimates showed that the population peaked during early spring and summer. Survival probability related to age, while temperature negatively affected recapture probability. Wing size varied throughout the study similarly for males and females, and both sexes displayed similar mobility. The distribution of flowers along sampling transects was not homogenous; Aristolochia sessilifolia was the only host plant recorded. The number of butterfly captures was higher in meadows and shrublands when compared to swamplands. Both the presence of flowers and host plants increased the chances of capturing individuals. The results shown here are relevant to design conservation strategies for the species, suggesting that classic conservation strategies, aimed to maintain a single patch of habitat protecting a single population, may not be the best strategy for the E. corethrus.