Application of DNA metabarcoding in the dietary pattern of a nonbreeding white-tailed eagle population in Northeast Asia under supplementary feeding

Food supplementation has become an increasingly prevalent strategy for animal conservation. A large white-tailed eagle (Haliaeetus albicilla) population exists in a wetland in Northeast Asia during the boreal winter, mainly because of regular supplementary feeding. However, the use of supplementary food by eagles has not been assessed. In this study, we used non-invasive sampling and DNA metabarcoding to investigate the food composition of white-tailed eagles in a lake near a supplementary feeding site. Our results revealed that supplemental food was present in 94 % of the samples, with a weighted percent of occurrence (wPOO) of 64.62 %. In addition to supplementation, we identified 11 natural prey species, including fish, birds, and mammals, from freshwater, marine, and terrestrial ecosystems. After February, there was an increasing trend in the frequency of natural food items, especially of marine fish, in the diet of the eagles. Our study demonstrates the power of DNA metabarcoding in dietary studies of raptor species in the presence of supplementary feeding. Based on our results, multiple recommendations have been provided to achieve adaptive management of large nonbreeding populations of eagles in our study area.