AIM: For many migratory avian species, winter and breeding habitats occur at geographically distinct locations. Disparate magnitudes and direction of shifts in wintering and breeding locations could lead to altered migration distances. We investigated how shifts in the centre of abundance (COA) of winter and breeding ranges have changed for 77 species of short‐distance migratory birds. We addressed whether species tracked their historical average temperature and precipitation conditions at their winter and breeding COA, using data from 1990 to 2015. LOCATION: North America. METHODS: We calculated the COA for winter and breeding ranges from the National Audubon Society's Christmas Bird Count and the North American Breeding Bird Survey. We regressed the annual change in distance (km) between the two annual COAs of each species as a proxy for change in migration distance. We constructed a series of generalized linear mixed models (GLMMs) to evaluate changes in average temperature and precipitation at the wintering and breeding COAs. RESULTS: Winter shifts in COA were predominantly northward. For most species, average temperature and precipitation that species experienced had not changed. Breeding shifts in COA varied in direction. For breeding season COAs, average temperature warmed, but average precipitation had not changed. Thirty‐one species significantly decreased their migration distances, mainly driven by northward shifts in the winter range. Ten species increased their migration distances. MAIN CONCLUSIONS: Winter and breeding range shifts in COA have not occurred at the same magnitude and direction and have therefore impacted migration distance. Our results suggest that wintering and breeding range shifts occur independently and under different climate pressures.

中文翻译：

---

冬季差异和繁殖范围变化：对鸟类迁徙距离的影响

目的：对于许多迁徙鸟类而言，冬季和繁殖栖息地发生在地理上不同的位置。越冬和繁殖地点变化的不同幅度和方向可能导致迁徙距离的改变。我们调查了 77 种短距离候鸟的冬季丰度中心 (COA) 和繁殖范围的变化。我们使用 1990 年至 2015 年的数据，解决了物种在冬季和繁殖 COA 时是否跟踪其历史平均温度和降水条件的问题。地点：北美。方法：我们根据国家奥杜邦协会的圣诞鸟类计数和北美育种鸟类调查计算了冬季和繁殖范围的 COA。我们回归了每个物种两次年度 COA 之间距离（​​km）的年度变化，作为迁移距离变化的代表。我们构建了一系列广义线性混合模型 (GLMMs) 来评估越冬和繁殖 COA 平均温度和降水的变化。结果：COA 的冬季移动主要是向北移动。对于大多数物种，物种经历的平均温度和降水没有改变。COA 的育种变化方向不同。对于繁殖期COA，平均气温升高，但平均降水量没有变化。31 个物种的迁徙距离显着减少，主要是由于冬季范围内的北移。十个物种增加了它们的迁徙距离。主要结论：COA 的冬季和繁殖范围的变化没有以相同的幅度和方向发生，因此影响了迁移距离。我们的结果表明越冬和繁殖范围的变化是独立发生的，并且是在不同的气候压力下发生的。