Seasonal Variation in Nocturnal Roost Timing and Diurnal Movement in Endangered Crested Ibis (Nipponia nippon): An Adaptation Strategy to Environmental Changes

The living environment of birds exhibits seasonal variations, and winter cold and food shortages are key limiting factors influencing the survival rate of many bird species. However, most previous studies have focused on dynamic habitat changes, with relatively few investigating how changes in birds' behavioral rhythms and ecological adaptability respond to seasonal fluctuations in the environment. The Crested Ibis (<i>Nipponia nippon</i>) is an endangered species, with winter food shortage being a critical factor constraining its population growth. Through 211 days of monitoring on the communal roosting behavior and GPS tracking of 19 individuals, this study aimed to clarify seasonal variations in their time allocation and activity levels, and reveal how Crested Ibises respond to environmental changes. During the wintering period, Crested Ibises departed nocturnal roosts earlier relative to sunrise and returned later relative to sunset, thereby utilizing more dawn and dusk time for foraging and increasing daylight utilization. GPS tracking data showed that both daily movement distance and activity levels of Crested Ibises during the wintering period were significantly lower than in other seasons-a pattern likely representing an adaptive strategy to cope with limited food resources, as it serves to minimize energy expenditure and enhance survival rates. Thus, these findings indicate that Crested Ibises adapt to wintering environmental changes through three seasonal behaviors: extending the dawn and dusk activity window, increasing daylight utilization, and reducing daily movement distance and activity levels.