Fecal DNA metabarcoding reveals the dietary composition of wintering Red-crowned Cranes (Grus japonensis)

Understanding the diet of threatened wildlife is vital for species-specific conservation and habitat management measures. The Red-crowned Crane (Grus japonensis) is a vulnerable bird distributed in Northeast Asia. Previous dietary studies of this bird focused mainly on its plant food composition based on field observations and microhistological identification. Herein, a total of 45 fecal samples were collected in November, December and January (15 fecal samples each month) from wintering cranes, and then subjected to a high throughput sequencing meta-barcoding approach to determine the primary plant (rbcL) and animal (COI) food items in their diet. A total of 230 operational taxonomic units (OTUs) of plant foods and 371 OTUs of animal foods were obtained. The main plant foods in the wintering period were Miscanthus, Zea, and Hordeum genera, which were similar to those in the breeding and the migration periods. Both agricultural and natural plants were detected, indicating a relatively broad dietary niche for this crane species. However, the main animal foods were representatives of Theridiidae, Megascolecidae, and Agelenidae, in sharp contrast to previous studies. The higher number of small terrestrial arthropods in animal foods might be due to the indirect intake of plants. The composition of both plant and animal foods in the diet showed the highest diversity in December, while it was homogeneous in January. The plant of Zea genus became the main source of nutrition in late winter, as supplementary feeding was performed in the reserve, which could help Red-crowned Cranes to get through the cold season. The results obtained in this work would contribute to the development of effective conservation strategies for the Red-crowned Crane.