Carrying capacity of black‐necked cranes in Dashanbao National Nature Reserve, China

Abstract

AbstractSince 2005, large areas have been planted for maca, the introduced cash crop, on cropland and grassland in Yunnan, China. While cash crops offer clear economic benefits over conventional crops, they also reduce the amount of land for wildlife, especially wading birds. The effect of cash crops on the energetic carrying capacity for birds requires evaluation. The black‐necked crane (Grus nigricollis) is a flagship species wintering in northeast and northwest Yunnan where large areas of cropland and grassland have been converted to maca production. Understanding changes in the energetic carrying capacity in response to increasing maca production will facilitate the development of effective conservation plans for the protection of black‐necked cranes. We estimated food density and the crane's daily energy requirements by observing the foraging behavior of crane individuals using telescopes and recorded video to measure the energetic carrying capacity of the black‐necked crane in the Dashanbao National Nature Reserve. The monthly energetic carrying capacity was similar between the pre‐expansion planting period for maca (2012–2014) and the expansion planting period (2014–2015). The abundance of invertebrates in grassland in December and January and Tartary buckwheat in March was below the food density threshold (below which foraging becomes energetically unprofitable) in both the pre‐and post‐maca planting years. In addition, the crop yield was significantly affected by freeze damage in spring. Thus, climate and abundance of invertebrates affect the energetic carrying capacity of black‐necked cranes in Dashanbao Reserve. We suggest that the local relevant departments should fully assess the potential effect on the cranes when implementing the large‐scale cultivation of introduced crops and avoid the large‐scale planting of single‐species crops. The largest planted area in suitable farmland within the study area should not exceed 1,000 ha. Maca planting should be undertaken with caution in this area because of the potential effect on black‐necked cranes.