Adult male birds advance spring migratory phenology faster than females and juveniles across North America

Advances in spring migratory phenology comprise some of the most well-documented evidence for the impacts of climate change on birds. Nevertheless, surprisingly little research has investigated whether birds are shifting their migratory phenology equally across sex and age classes – a question critical to understanding the potential for trophic mismatch. We used 60-years of bird banding data across North America – comprising over 4 million captures in total – to investigate both spring and fall migratory phenology for a total of 98 bird species across sex and age classes, with the exact numbers of species for each analysis depending on season-specific data availability. Consistent with protandry, in spring (n=89 species), adult males were the first to arrive and immature females were the last to arrive. In fall (n=98), there was little difference between sexes, but adults tended to depart earlier than juveniles. Over 60 years, adult males advanced their phenology the fastest (-0.84 days..., See Methods of Neate-Clegg & Tingley, Global Change Biology. Briefly, raw banding data were extracted from the USGS Bird Banding Lab. A series of stringent filters were applied to narrow the dataset down to meet sample size requirements. Then, Weibull-corrected phenological metrics were calculated for every age group and sex for every species., ,

春季迁徙物候的相关研究进展，是证实气候变化对鸟类影响的最充分有据可查的证据之一。然而，鲜有研究探讨鸟类的迁徙物候变化是否在不同性别和年龄组间保持一致——这一问题对于理解营养级错配（trophic mismatch）的潜在可能性至关重要。本研究依托北美地区60年的鸟类环志数据（总捕获量超400万次），针对98种鸟类的不同性别和年龄组，分别探究其春季和秋季迁徙物候；每项分析所涉及的具体物种数量，取决于对应季节的数据可获得性。与雄性先熟（protandry）现象一致，在春季（分析涉及89个物种），成年雄鸟最早抵达，未成熟雌鸟最晚抵达。秋季（分析涉及98个物种）时，不同性别间差异较小，但成年个体往往比幼鸟更早离开。在60年的时间跨度中，成年雄鸟的物候提前速度最快（-0.84天……详见Neate-Clegg与Tingley发表于《Global Change Biology》的研究方法部分）。简言之，原始环志数据取自美国地质调查局鸟类环志实验室（USGS Bird Banding Lab），随后通过一系列严格的筛选步骤缩小数据集规模以满足样本量要求，最终针对每个物种的各年龄组与性别，计算经威布尔（Weibull）校正的物候指标。