Blood-feeding is one of the most specialized foraging habits, as it demands extreme morphological, physiological, and behavioral adaptations. Three species of vampire bats (Desmodus rotundus, Diaemus youngi, and Diphylla ecaudata) rely on blood as their only food. The first two are considered less specialized, whereas D. ecaudata is frequently pointed out as a bird-specialist. We assessed what prey D. ecaudata consumes in the Caatinga dry forests of northeastern Brazil, a highly modified biome. How the species would behave in a situation of scarcity of wild birds and increase in the availability of domestic animals? Could Diphylla have been induced to include also mammals in its diet? Using PCR-amplification of DNA fragments in the feces of D. ecaudata, we detected the regular consumption of chicken blood and human blood — a novel prey for this species. Our results suggest that the diet of D. ecaudata is more flexible than expected. The record of humans as prey and the absence of blood from native species may reflect a low availability of wild birds in the study site, reinforcing the impact of human activities on local ecological processes. This also opens a range of research possibilities on vampire bats in the Caatinga, both on the species' biology and the consequences for public health, considering the potential increase in the transmission of rabies in the region.