The effects of temporal and spatial variations in food resources on the distribution and abundance of Black-necked Cranes, Grus nigricollis

Abstract The Black-necked Crane, Grus nigricollis, is categorized as Vulnerable on the IUCN Red List. Food distribution and biomass are factors that will determine its long-term survival. Understanding food variation will facilitate the development of effective conservation plans for the protection of this vulnerable species. Available biomass of food for Black-necked Cranes was sampled on the agricultural farmlands and grasslands used by foraging flocks of these species in Dashanbao Nature Reserve, during the winter periods of 2012 and 2015. We compared variation separately in biomass of a particular group (e.g. invertebrates, grains and potato) and analysed the relationship between food biomass utilisation by cranes. The results showed that relative availability of invertebrates in grassland, and potato and grain in farmland, varied seasonally. The number of cranes was less affected by the monthly food variation in the reserve. However, the habitat type has an impact on the number of cranes. In grassland habitat, crane abundance was positively related to invertebrate biomass. However, there was no significant correlation in farmland habitat. Availability food in both habitats vary across years, months, which relate to a seasonal crop depletion and farming, and annual to crop productivity, and invertebrate availability, influenced in part by winter temperatures. Therefore, we recommend that there should be enough food biomass in the reserve for cranes to forage during the cold-weather periods, and expanded grassland foraging habitat, so as to expand the range of foraging and increase the diversity of food for the cranes.