Reduced prey abundance and severe weather can lead to a greater risk of mortality for seabirds during the non-breeding winter months. Resource patterns in some regions are shifting and becoming more variable in relation to past conditions, potentially further impacting survival and carryover to the breeding season. As animal tracking technologies and methods to analyze movement data have advanced, it has become increasingly feasible to draw fine-scale inference about how environmental variation affects foraging behavior and habitat use of seabirds during this critical period. Here, we used archival light-sensing tags to evaluate how interannual variation in oceanography affected the winter distribution of Cassin's Auklets from Southeast Farallon Island, California. Thirty-five out of 93 geolocators deployed from 2015 to 2017 were recovered and successfully recorded light-level data, from which geographic positions were estimated. Step-selection functions were applied to identify environmental covariates that best explained winter movement decisions and habitat use, revealing Cassin's Auklets dispersed farther from the colony during a winter with warm SST anomalies, but remained more centralized near the breeding colony during two average winters. Movement patterns were driven by avoidance of areas with higher sea surface temperatures and possible limits of dispersal from the breeding colony, and selection for areas with well-defined mesoscale fronts and cooler surface waters. Through multiple years of tagging and the application of step-selection functions, a robust and widely applied approach for analyzing animal movement in terrestrial species, we show how interannual differences in the movement patterns of a small seabird are driven by oceanographic variability across years. Understanding the winter habitat use of seabirds can help inform changes in population structure and measures of reproductive success, aiding managers in determining potential causes of breeding failures.

中文翻译：

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卡辛​​（Cassin）的Auklets中冬季栖息地的海洋学驱动因素。

在冬季非繁殖季节，猎物数量的减少和恶劣天气会导致海鸟更大的死亡风险。与过去的状况相比，某些地区的资源格局正在发生变化，并且变得更加可变，有可能进一步影响生存和结转到繁殖季节。随着动物跟踪技术和用于分析运动数据的方法的发展，在此关键时期，关于环境变化如何影响海鸟的觅食行为和栖息地使用的小规模推断已变得越来越可行。在这里，我们使用了存档的光敏标签来评估海洋学中的年际变化如何影响来自加利福尼亚东南法拉隆岛的卡辛Auklets的冬季分布。从2015年到2017年部署的93个地理定位器中，有35个被恢复并成功记录了光水平数据，据此可以估算地理位置。应用了分步选择功能来识别最能解释冬季运动决策和栖息地使用的环境协变量，揭示出在具有温暖的SST异常的冬季，Cassin的Auklets散布在远离殖民地的地方，但在平均两个冬季期间仍在繁殖地附近更加集中。避开具有较高海表温度的区域以及可能从繁殖群体扩散的限制，以及选择具有明确中尺度锋面和地表水较凉爽区域的区域来驱动运动模式。通过多年的标记和分步选择功能的应用，一种用于分析陆生物种动物运动的强大而广泛应用的方法，我们展示了小海鸟运动模式的年际差异是如何受到多年来海洋学变化的驱动。了解海鸟在冬季栖息地的用途可以帮助了解种群结构的变化和繁殖成功的措施，帮助管理人员确定繁殖失败的潜在原因。