Time budget and behavioral rhythm of animals can be regarded as a kind of behavioral adaptation to environmental conditions. The Black-necked Crane (Grus nigricollis) use fixed roosting sites during overwintering periods and have a daily behavioral pattern of flying out from the roosting sites in the morning to forage and flying back in the evening to roost. To explore the time budget and factors influencing this behavior during different periods of winter, a field study by means of instantaneous scan sampling was conducted on the flight and behavior patterns of Black-necked Cranes at seven roosting sites at the Caohai wetland. The field observations were conducted in the whole winter, which divided into three periods: early winter (Nov. 9﹣Dec. 31), mid-winter (Jan. 1﹣Feb. 21) and late winter (Feb. 22﹣Mar. 31). Based on the known behavioral spectrum of Black-necked Cranes and previous observation results (Li et al. 2005), crane behavior at roosting sites before the morning departure and after the evening return was classified into 8 categories and 14 types (Table 1). One-way analysis of variance (ANOVA) was used to test the time differences of the daily departure and return flights between three periods of winter. The results showed that both departure and return times were significantly different between the three periods. Compared with early winter, the departure time from roosting sites was delayed in middle winter and advanced in late winter (mean times: 7:34, 7:40, and 7:13 in the morning), while the return time to roosting sites became gradually later throughout the winter (from 17:12 to 18:15 in the late afternoon) (Fig. 2). A Chi-square R × C table test was used to compare patterns of the departure and return times from roosting sites as well as the behavioral differences before departure and after return between different periods of winter. There was a significant difference of the behavior before departure among early, mid, and late winter (F = 1 768.25, df = 12, P < 0.01), so as to the behavioral differences after their return to the roosting sites (F = 793.98, df = 12, P < 0.01). The behavior of the cranes before the morning departure and after the evening return was significantly different in the early winter period (F = 2 723.16, df = 6, P < 0.01), mid-winter period (F = 1 979.48, df = 6, P < 0.01), and late winter period (F = 5 098.18, df = 6, P < 0.01) (Table 2). The occurrence frequency of various types of behavior in the crane roosting population within 80 min before morning departure and 90 min after evening return were recorded. For the 80-minute period before the morning departure from the roosting site, maintaining (34.32%) and resting (32.38%) were the dominant behaviors, while foraging (43.04%) and resting (23.68%) were the dominant behaviors within the 90-minute period after the evening return (Fig. 3). The Pearson correlation coefficient was used to test the correlation between the flight times and the sunrise and sunset times. The departure times were significantly related with sunrise time (r = 0.832, n = 48, P < 0.01), while the return times were weakly correlated with sunset time (r = 0.353, n = 47, P < 0.01). Multiple linear regression analysis was used to test the effects of temperature and humidity on the departure and return time changes. The difference between the sunrise time and the crane departure time (Y1) was affected by humidity at the time of the departure (W) (Y1 = 0.469﹣0.625W, P < 0.05). The difference between the sunrise time and the crane departure time (Y1) was inversely proportional to humidity at the time of departure (W). The difference between the sunset time and the crane return time (Y2) was affected by mean daily temperature (T) (Y2 = 1.231﹣0.107T, P < 0.05). Our results can be meaningful and useful for further exploring the roosting behavior of Black-necked Cranes as well as their behavioral adaptations to human disturbances.