Least intrusive sampling should be prioritized for wildlife conservation and bioethics. In birds, DNA samples are typically obtained from blood. Here we emphasized buccal swabs as an alternative source. We tested swabs in adults and nestlings representative of 17 European species (n 189), ranging from small passerines to large Strigiformes (owls) and Larids (gulls), and characterized the extracted DNA yields. The contents were highly variable between and within species, both in terms of quantity and perhaps purity, but the amounts obtained (-100— 10,000 ng) meet the requirements of standard molecular analyses. No differences were found between adults and nestlings. The DNA yields were moderately higher for larger bird species, and samples taken from experienced swabbers yielded more DNA. In line with species-specific case studies that had successfully implemented buccal swabs, our results support the universal potential of the technique, which should be more generally applied in avian research, notably when endangered species are involved.