Bird migration is often framed as a straightforward journey between one breeding site and one wintering site, but recent research has shown that the reality is often more complex. Many species of birds undertake short‐distance movements separate from long‐distance migration. Such movements appear to be common in species that breed in western North America, where mountainous terrain creates a mosaic of habitats and climatic conditions. However, individual‐based tracking studies have disproportionately focused elsewhere, leaving gaps in our understanding of the year‐round movements of western species. I used tracking data from light‐level geolocators and citizen science data from eBird to study the movements of Cassin’s Vireos (Vireo cassinii) breeding in the Sierra Nevada mountains of California, USA. During three breeding seasons (2013–2015), my observations suggested that Cassin’s Vireos vacate their breeding territories during the post‐breeding period in July and August. In April and May 2016, I tagged 22 Cassin’s Vireos with light‐level geolocators and, in April and May 2017, recaptured four that had retained their geolocators. Geolocator data showed that these four birds remained in the same geographic region as their breeding territories (likely the same mountain range) during the post‐breeding period in July and August 2016, ruling out the possibility of long‐distance movements during this time. Analysis of eBird citizen science data suggested that Cassin’s Vireos undertake short‐distance molt‐migration to higher elevations in the Sierra Nevada Mountains during the post‐breeding period. Geolocator data revealed that long‐distance fall migration took place in September and spring migration in April or May, and the four birds spent the winter in different parts of the Mexican winter range of Cassin’s Vireos. These results add to the body of literature on the complex movements of migratory songbirds breeding in the mountains of western North America, an understanding that will be important for effective conservation in the future.

中文翻译：

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卡辛​​的维雷奥斯的长距离运动和繁殖后高程运动的证据

鸟类迁徙通常被认为是在一个繁殖地点和一个越冬地点之间进行的直截了当的旅程，但是最近的研究表明，现实往往更加复杂。许多鸟类会进行与远距离迁徙分开的近距离运动。这种运动在北美西部繁殖的物种中似乎很常见，那里的山地地形形成了栖息地和气候条件的马赛克。但是，基于个体的跟踪研究不成比例地集中在其他地方，这使我们对西方物种全年运动的理解存在差距。我使用了来自轻型地理定位器的跟踪数据和来自eBird的公民科学数据来研究卡辛的维雷奥斯（Vireo cassinii）的运动）在美国加利福尼亚的内华达山脉中繁殖。在三个繁殖季节（2013-2015年），我的观察结果表明，卡辛的维雷奥斯犬在7月和8月的繁殖后期腾出了繁殖区域。在2016年4月和2016年5月，我用轻型地理定位器标记了22个Cassin的Vireos，并在2017年4月和2017年5月重新夺回了四个保留其地理定位器的位置。Geolocator的数据显示，在2016年7月和2016年8月的繁殖后期间，这四只鸟与繁殖地区保持在相同的地理区域（可能是相同的山脉），排除了这段时间内长距离运动的可能性。对eBird公民科学数据的分析表明，在繁殖后的时期，卡辛的维雷奥斯人进行了短距离的蜕皮迁移至内华达山脉的更高海拔。Geolocator的数据显示，长距离秋季迁徙发生在9月，春季迁徙发生在4月或5月，这四只鸟在墨西哥卡辛维雷奥斯冬季范围的不同区域度过了冬季。这些结果增加了关于在北美西部山区繁殖的迁徙鸣鸟的复杂运动的文献，这一认识对于将来进行有效的保护非常重要。四只鸟在墨西哥卡辛维雷奥斯冬季范围的不同区域度过了冬季。这些结果增加了关于在北美西部山区繁殖的迁徙鸣鸟的复杂运动的文献，这一认识对于将来进行有效的保护非常重要。四只鸟在墨西哥卡辛维雷奥斯冬季范围的不同区域度过了冬季。这些结果增加了关于在北美西部山区繁殖的迁徙鸣鸟的复杂运动的文献，这一认识对于将来的有效保护将是重要的。