Boyd Brendan P, Hayes Sue M, Migotto Anna Agazzi, Stutchbury Bridget J M
Department of Biology, York University, Toronto, Canada.
Mov Ecol. 2025 May 6;13(1):32. doi: 10.1186/s40462-025-00556-3.
Juvenile passerines are expected to have lower migration performance than adults due to their inexperience with long-distance flights and morphological limitations, such as shorter wing length. From 2016 to 2019 we radio-tagged nestling and adult Wood Thrushes (Hylocichla mustelina) at a breeding site in southwestern Ontario and used the automated Motus Wildlife Tracking System to test if age class predicts timing of the onset of fall migration (date, time of night), flight speed during the initial migration flight across Lake Erie, and overall pace of migration southward through the eastern United States. We detected 60/117 (51%) adults and 82/119 (69%) juveniles departing the breeding area as they initiated fall migration. Compared with adults, juveniles departed at an earlier date in fall and later time in the evening. When crossing Lake Erie on their first migratory flight juveniles travelled about 25% slower than adults but this was due primarily to adults making better use of tailwinds. When travelling south through the eastern U.S. juveniles had a slower overall migration pace (47.3 ± 5.1km/day) than adults (71.6 ± 4.7km/day). Although we found evidence that juvenile Wood Thrushes have an earlier and slower fall migration than adults, identifying the proximate and ultimate mechanisms remains a challenge. There is no evidence that juvenile Wood Thrushes are inefficient in migration flight or refueling at stopovers, and it is unlikely that the fall migration pace in this species affects their ability to compete for wintering food resources. More tracking studies from breeding sites are needed to understand the ecological factors favouring and biological significance of, age-related differences in migration performance.
由于幼龄雀形目鸟类缺乏长途飞行经验以及存在形态学上的限制，如翅长较短，预计它们的迁徙表现会低于成年鸟类。2016年至2019年期间，我们在安大略省西南部的一个繁殖地为雏鸟和成年伍德 Thrush（Hylocichla mustelina）佩戴无线电标签，并使用自动化的Motus野生动物追踪系统来测试年龄组是否能预测秋季迁徙开始的时间（日期、夜间时间）、首次穿越伊利湖的迁徙飞行速度以及向南穿越美国东部的总体迁徙速度。在开始秋季迁徙时，我们检测到60/117（51%）的成年鸟和82/119（69%）的幼鸟离开繁殖区域。与成年鸟相比，幼鸟在秋季更早的日期和更晚的夜间时间离开。在首次迁徙飞行穿越伊利湖时，幼鸟的飞行速度比成年鸟慢约25%，但这主要是因为成年鸟能更好地利用顺风。当向南穿越美国东部时，幼鸟的总体迁徙速度（47.3±5.1公里/天）比成年鸟（71.6±4.7公里/天）慢。尽管我们发现有证据表明幼龄伍德 Thrush的秋季迁徙比成年鸟更早且更慢，但确定其近端和最终机制仍然是一个挑战。没有证据表明幼龄伍德 Thrush在迁徙飞行或中途停留觅食时效率低下，而且该物种秋季的迁徙速度不太可能影响它们竞争冬季食物资源的能力。需要更多来自繁殖地的追踪研究来了解有利于迁徙表现年龄相关差异的生态因素及其生物学意义。
