Herring Gulls (Larus Argentatus); Clark; Massachussets United States-gps

Background: Recent studies have proposed that birds migrating short distances migrate at an overall slower pace, minimizing energy expenditure, while birds migrating long distances minimize time spent on migration to cope with seasonal changes in environmental conditions. Methods: We evaluated variability in the migration strategies of Herring Gulls (Larus argentatus), a generalist species with flexible foraging and flight behaviour. We tracked one population of long distance migrants and three populations of short distance migrants, and compared the directness of their migration routes, their overall migration speed, their travel speed, and their use of stopovers. Results: Our research revealed that Herring Gulls breeding in the eastern Arctic migrate long distances to spend the winter in the Gulf of Mexico, traveling more than four times farther than gulls from Atlantic Canada during autumn migration. While all populations used indirect routes, the long distance migrants were the least direct. We found that regardless of the distance the population traveled, Herring Gulls migrated at a slower overall migration speed than predicted by Optimal Migration Theory, but the long distance migrants had higher speeds on travel days. While long distance migrants used more stopover days overall, relative to the distance travelled all four populations used a similar number of stopover days. Conclusions: When taken in context with other studies, we expect that the migration strategies of flexible generalist species like Herring Gulls may be more influenced by habitat and food resources than migration distance.

研究背景：近期研究提出，短途迁徙鸟类整体迁徙节奏更为缓慢，以最小化能量消耗；而长途迁徙鸟类则会尽量压缩迁徙耗时，以应对环境条件的季节性变化。研究方法：本研究针对觅食与飞行行为灵活的广适性物种——银鸥（Herring Gulls, Larus argentatus）的迁徙策略变异情况展开评估。我们对1个长途迁徙种群与3个短途迁徙种群进行追踪，对比了其迁徙路线的直达性、整体迁徙速度、行进速度以及中途停歇地的利用情况。研究结果：本研究发现，繁殖于北极东部的银鸥会进行长距离迁徙，前往墨西哥湾越冬，其秋季迁徙的总路程是加拿大大西洋沿岸银鸥的4倍以上。尽管所有种群均采用非直达迁徙路线，但长途迁徙种群的路线直达性最差。研究表明，无论迁徙距离长短，银鸥的整体迁徙速度均低于最优迁徙理论（Optimal Migration Theory）的预测值，但长途迁徙种群在实际飞行日的速度更快。尽管长途迁徙种群的总停歇天数更多，但以迁徙距离为基准归一化后，四个种群的停歇天数并无显著差异。研究结论：结合其他同类研究来看，我们推测，诸如银鸥这类行为灵活的广适性物种，其迁徙策略所受栖息地与食物资源的影响，可能大于迁徙距离本身的作用。