Resource availability, particularly food, can limit the size of bird populations during the nonbreeding season. Resident and short-distance migrant birds, wintering in colder environments, should show strong effects of food limitation on winter survival. Here, we introduce a novel experiment testing for the effect of supplemental feeding on the winter survival of the Dark-eyed Junco (Junco hyemalis), a short- to medium-distance migrant in North America. Color-ringed juncos were monitored by resighting in the winters of 2011, 2012, and 2013. Winter supplemental feeding significantly increased junco survival within winters. However, it is possible that juncos not resighted underwent within-winter dispersal rather than died. Thus, in the winter of 2014, very high frequency radio transmitters were attached to 29 juncos from unsupplemented sites to ascertain the fate of birds not resighted. We found that movement beyond the study area was minimal and most juncos maintained a discrete home range. Of the radiotagged birds, 27.5% were not resighted during observation periods, but were located and confirmed alive via radiotracking. A correction factor for within-winter dispersal was applied to previous years’ data and the effect of food supplementation remained statistically significant for two of the three winters; the trend was the same, but not statistically significant during the warmest winter. The present results contribute to a developing conceptual model of migration-specific effects of winter food limitation. Dark-eyed Juncos are an iconic backyard birdfeeder species that have shown a steady population decline for decades. Supplemental feeding during the wintering period may regularly elevate population recruitment by increasing winter survival in avian species that winter in thermally challenging environments.

中文翻译：

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无线电跟踪改进了食物补充剂对黑眼 Junco (Junco hyemalis) 越冬生存的作用

在非繁殖季节，资源的可用性，尤其是食物，可以限制鸟类的数量。常驻和短距离候鸟在较冷的环境中越冬，食物限制对冬季生存的强烈影响。在这里，我们介绍了一项新的实验，用于测试补充喂养对北美中短距离迁徙黑眼鹱（Junco hyemalis）冬季生存的影响。在 2011 年、2012 年和 2013 年的冬季通过重新瞄准监测了色环 junco。冬季补充喂养显着增加了冬季内的 junco 存活率。然而，没有重新观察的 juncos 有可能在冬季传播而不是死亡。于是，在 2014 年的冬天，来自未补充地点的 29 个 juncos 连接了甚高频无线电发射器，以确定未重新观察的鸟类的命运。我们发现超出研究区域的移动很小，大多数 juncos 保持离散的家庭范围。在放射性标记的鸟类中，27.5% 在观察期间没有被重新观察，但通过无线电跟踪被定位并确认活着。对前几年的数据应用了冬季内扩散的校正因子，在三个冬季中的两个冬季，食品补充剂的影响在统计上仍然显着；这种趋势是相同的，但在最温暖的冬季没有统计学意义。目前的结果有助于开发冬季食物限制的特定迁移影响的概念模型。黑眼睛的 Juncos 是一种标志性的后院喂鸟物种，几十年来，该物种的数量一直在稳步下降。越冬期间的补充喂养可能会通过增加在热挑战环境中越冬的鸟类的冬季存活率来定期增加种群补充。