Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
Department of Coastal Systems, NIOZ Royal Institute for Sea Research and Utrecht University, Texel, the Netherlands.
J Anim Ecol. 2021 May;90(5):1058-1070. doi: 10.1111/1365-2656.13431. Epub 2021 Feb 9.
As environmental conditions fluctuate across years, seasonal migrants must determine where and when to move without comprehensive knowledge of conditions beyond their current location. Animals can address this challenge by following cues in their local environment to vary behaviour in response to current conditions, or by moving based on learned or inherited experience of past conditions resulting in fixed behaviour across years. It is often claimed that long-distance migrants are more fixed in their migratory behaviour because as distance between breeding and wintering areas increases, reliability of cues to predict distant and future conditions decreases. While supported by some population-level studies, the influence of migration distance on behavioural variation is seldom examined on an individual level. Lesser black-backed gulls Larus fuscus are generalist seabirds that use a diversity of migration strategies. Using high-resolution multi-year GPS tracking data from 82 individuals from eight colonies in Western Europe, we quantified inter- and intra-individual variation in non-breeding distributions, winter site fidelity, migration routes and timing of migration, with the objectives of determining how much variation lesser black-backed gulls have in their migratory behaviour and examining whether variation changes with migration distance. We found that intra-individual variation was significantly lower than variation between individuals for non-breeding distributions, winter site fidelity, migration routes and timing of migration, resulting in consistent individual strategies for all behaviours examined. Yet, intra-individual variation ranged widely among individuals (e.g. winter site overlap: 0-0.91 out of 1; migration timing: 0-192 days), and importantly, individual differences in variation were not related to migration distance. The apparent preference for maintaining a consistent strategy, present in even the shortest distance migrants, suggests that familiarity may be more advantageous than exactly tracking current environmental conditions. Yet, variation in behaviour across years was observed in many individuals and could be substantial. This suggests that individuals, irrespective of migration distance, have the capacity to adjust to current conditions within the broad confines of their individual strategies, and occasionally, even change their strategy.
由于环境条件在多年间波动，季节性迁徙者必须在不完全了解当前位置以外条件的情况下确定移动的地点和时间。动物可以通过跟随其当地环境中的线索来改变行为以响应当前条件，或者通过基于过去条件的学习或遗传经验来移动，从而在多年间形成固定行为。人们常说，长距离迁徙者的迁徙行为更为固定，因为繁殖地和越冬地之间的距离增加，预测遥远和未来条件的线索的可靠性降低。虽然一些种群水平的研究支持这一观点，但迁徙距离对行为变化的影响很少在个体水平上进行检验。黑背鸥 Larus fuscus 是一种使用多种迁徙策略的普通海鸟。利用来自西欧 8 个繁殖地的 82 只个体的高分辨率多年 GPS 跟踪数据，我们量化了非繁殖期分布、越冬地栖息地忠诚度、迁徙路线和迁徙时间的个体间和个体内变化，目的是确定黑背鸥在迁徙行为方面有多少变化，并研究这种变化是否随迁徙距离而变化。我们发现，非繁殖期分布、越冬地栖息地忠诚度、迁徙路线和迁徙时间的个体内变化明显低于个体间变化，导致所有被研究行为的个体策略都保持一致。然而，个体内变化在个体间差异很大（例如，越冬地重叠：0-0.91；迁徙时间：0-192 天），重要的是，个体间变化的差异与迁徙距离无关。即使在最短距离的迁徙者中，也存在保持一致策略的明显偏好，这表明熟悉度可能比准确跟踪当前环境条件更有利。然而，许多个体的行为在多年间发生了变化，而且这种变化可能很大。这表明，个体无论迁徙距离如何，都有能力在其个体策略的广泛范围内适应当前条件，并且偶尔会改变其策略。
