Relations of Daily Activity Patterns to Age and Flock of Wintering Black-necked Crane (Grus nigricollis) at Napa Lake, Shangri-La in Yunnan
From October 2006 to May 2007, daily activity patterns and the relationship between time budget and age, wintering stage, flocking behavior of Black-necked Cranes were studied at Napa Lake Nature Reserve, Shangri-La of Yunnan Province. We compartmentalized the winter season into three stages based on the amount of change the Black-necked Crane habited on Napa Lake Nature Reserve. The statistics from test results show significant differences among different stages in foraging, vigilance, preening, resting, locomotion, aggression, and flying (F2,36= 4.63–26.54, χ2222= 5.29–13.68, P= 0.0016–0.000). During the study period, Black-necked cranes devoted most of their daily activity time to foraging , which is about 76.81±9.1%. The percent time spent foraging showed two peaks; one peaking in the middle morning and another higher peak during late afternoon. The postponing of higher foraging peaks is a behavioral adjustment in response to the frigid weather of morning. Adult Black-necked Cranes showed significant differences in foraging, vigilance and aggression between flocks and families(F1,76= 0.27, 0.77, U= 279, P= 0.001–0.000), but there were no significant differences in juveniles(U=735–558, P=0.924–0.062). Adults foraging in flocks showed an advantage for having more foraging time and less vigilance than family-based units. Juveniles spent more time in foraging and resting compared to adults, with less time in vigilance and aggression contrary. There are differences with wintering behavior between various wintering areas. We explain these activity changes as a consequence of a behavioral adaptation to the local environment changes, while climate and food resources are important factors that affect wintering behavior.