Number, Habitats, and Roosting Sites of Wintering Black-necked Cranes in Huize Nature Reserve, Yunnan, China

摘要

The black-necked crane (Grus nigricollis, BNC), a migratory bird classified as vulnerable under the revised IUCN Red List, faces serious threats from human activities and habitat degradation. We measured the changes in the number, habitats, and roosting sites of wintering BNCs in Huize Nature Reserve, northeast Yunnan, China, based on remote sensing images from 1992 and 2006 and field data from 1991 to 2009. The wintering BNCs foraged collectively in muddy bottomlands and cultivated fields. The number of BNCs increased from 320 in 1991 to 738 in 2009, but their roosting sites decreased from 12 between 1990 and 1995 to 6 in 2009. Most BNCs, similar to what is described in other studies, spent nights in the wetlands; but some were forced to roost on dry hill slopes, an unusual roosting site for BNCs. From 1992 to 2006, cultivated fields increased from 17.35 to 34.45%, woodlands decreased from 40.89 to 35.80%, and shrublands decreased from 36.72 to 20.74%. Of the total usable food in BNC habitats, 65.8% was seeds and tubers—potato, turnips, and wild radish—found especially on the soils of muddy bottomlands and cultivated fields. We conclude that abundant food (especially potato residues) available near the surface of soils of traditionally cultivated fields benefits the survival of wintering BNCs and that the wintering BNCs are forced to choose new habitats for the nights when wetland habitats are degraded and human disturbance increases.