Roosting-site Selection by Overwintering Black-necked Cranes in the Caohai Wetland, Guizhou Province, China: Implications for Conservation Management.

Stable and high-quality roosting-sites are crucial for the survival of migratory wading birds in winter. The black-necked crane ( Grus nigricollis ) is the only crane species that lives on the Tibetan plateau for its entire life. Every year, black-necked cranes routinely migrate to the wetlands on the southern lower plateau and roost at wetland sites. Currently, many roosting-sites are under threat from wetland degradation resulting from human disturbance, and changes in water depths and the landscape environment. To understand how the black-necked crane selects roosting-sites given these influencing factors, we conducted a study in the Caohai wetland in China by comparing and modeling the selection of roosting habitat. The vegetation factors mainly included the vegetation height of the swamp patch where the roosting-site was located (VHP) and the vegetation height in the roosting-site (VHR), and the geographic factors mainly included the height of the nearest hill (HNH) and the visible range (VR). These four factors were first considered by the black-necked cranes when choosing roosting-sites on the lakeshore. The roosting-site selection model of black-necked cranes was fitted as ( P = e Logit ( p ) /(1 + e Logit ( p ) ) Logit( p ) = 1.243 + 8.397(VHP) -7.999(VHR) -4.105(HNH) + 1.584(VR)). In the Caohai wetland, black-necked cranes preferred roosting-sites away from human disturbances, such as villages/settlements and roads, and where the distance to main roads was > 1,300 m, the distance to villages/residential areas was > 650 m, the distance to rural/service roads was > 500 m, the relatively open area with surrounding hills had a relative height < 15 m, the visible range area was > 550,000 m2 , and the shallow swamp area had a water depth of < 5 cm with a vegetation height of < 15 cm. Outside the area of the roosting-site, the surrounding vegetation height was 35 cm-60 cm. We believe that human disturbance, not energy savings or heat loss, was the main factor influencing crane roost site selection. We first gathered data about black-necked crane selection of roosting-sites in a highly complex wetland system. Based on our findings, we strongly recommend appropriately managing the habitat patches in the Caohai wetland, which will have implications for the conservation management of overwintering black-necked cranes in wetlands.