Data and R codes for: Beyond circannual fattening: Behavioural flexibility and sex-specific strategies enable coping with high-elevation winters

Abstract Winter survival at high elevations imposes severe physiological and behavioural constraints on resident birds, necessitating specialised adaptations to cope with low temperatures, high energy demands, and limited food availability. We studied the White-winged Snowfinch (Montifringilla nivalis nivalis), a small passerine that inhabits high mountains year-round. Using GPS tracking and morphological measurements, we examined seasonal changes in body mass, fat reserves, muscle mass, and lean body mass, alongside movement behaviour. Our results showed that snowfinches maintain larger fat reserves than overwintering lowland passerines, with fat accumulation regulated mainly by a circannual programme, likely reflecting a physiological adaptation to the high-elevation environment. Seasonal behavioural plasticity, including sex-specific strategies and flexible movement patterns, appears to play an additional key role in coping with winter challenges in high mountains. Analysis of temperature effects on body mass indicated that fat accumulation is determined mainly by long-term rather than short-term fluctuations. These findings suggest that ongoing climate change, characterised by rising mean temperatures and more frequent extreme events, could disrupt this preparatory strategy, leading to reduced fat reserves and more frequent exposure to adverse winter and spring conditions.摘要 高海拔区域的冬季生存对留鸟施加了严苛的生理与行为约束，促使其演化出特化适应策略，以应对低温、高能量需求与食物匮乏的生存压力。本研究以常年栖息于高海拔山地的小型雀形目鸟类——白翅雪雀（Montifringilla nivalis nivalis）为研究对象，通过GPS追踪与形态学测量手段，分析了其体重、脂肪储备、肌肉质量与去脂体重的季节变化，并同步探究其运动行为模式。 研究结果表明，白翅雪雀的脂肪储备量高于越冬低海拔雀形目鸟类，其脂肪积累主要受年节律程序调控，这一特征大概率反映了其对高海拔环境的生理适应。季节性行为可塑性（包括性别特异性策略与灵活的运动模式）似乎是应对高海拔山地冬季挑战的另一关键支撑机制。针对温度对体重影响的分析显示，脂肪积累主要由长期温度波动而非短期波动决定。 上述研究结果提示，以平均气温上升与极端气候事件频发为特征的持续气候变化，可能会扰乱这一预适应储备策略，进而导致白翅雪雀的脂肪储备减少，且更频繁地暴露于恶劣的冬春环境条件中。