Our knowledge of the historical use of nonhuman animal species in captivity and subsequent human-induced changes in their distribution is poor in comparison to contemporary case studies. Here we assess the hypothesis that, in the case of one waterbird species, the purple swamphen or gallinule (Porphyrio porphyrio), we have neglected the high probability that people transported these birds within the Mediterranean, from Roman to recent times. In ancient iconographies, literary sources, and more recent records there is ample evidence for the use of this species in captivity, captive-breeding, and for trade during several historical periods, especially within the Mediterranean region. All this evidence supports the hypothesis that released or escaped birds might have hybridized with other populations living in the wild. This case study stresses the importance of taking into account past human activity when interpreting contemporary distributional patterns of species.