Department of Biology, Queen's University, Kingston, ON, Canada.
J Evol Biol. 2020 Apr;33(4):495-504. doi: 10.1111/jeb.13583. Epub 2020 Jan 20.
Migrant species are commonly thought to be poor competitors in aggressive interactions with resident species. However, no studies have tested whether this relationship is widespread. Here, we compare the behavioural dominance of closely related species of migratory and nonmigratory birds, testing whether migrants are consistently subordinate to resident species in aggressive contests. We compiled published behavioural dominance data involving migrant and resident congeners, gathering additional data on the body mass and migratory distance of each species. Focal species included a diverse array of birds (28 taxonomic families, 12 orders) from around the world. We found that migrant species are usually subordinate to resident species, but that this relationship disappears at larger body sizes. For smaller birds (<500 g), resident species were behaviourally dominant in 83%-88% of comparisons; for larger birds (>500 g), resident species were dominant in only 25%-30% of comparisons. The relative difference in body mass best predicted dominance relationships among species, with larger species dominant in 80%-84% of comparisons. When migrant and resident masses were equal, however, resident species were still more likely to be dominant in smaller birds, suggesting that other factors may also contribute to the subordinate status of migrants. Overall, our results suggest that in smaller species, the evolution of migration is associated with lighter weights and other traits that compromise the competitive abilities of migrants relative to residents. In contrast, larger species appear able to evolve migration without compromising their size or competitive abilities in aggressive contests, suggesting size-dependent constraints on the evolution of migration.
迁徙物种通常被认为在与居留物种的激烈竞争中处于劣势。然而，目前还没有研究测试这种关系是否普遍存在。在这里，我们比较了具有密切亲缘关系的迁徙和非迁徙鸟类物种的行为优势，以测试在激烈的竞争中，迁徙物种是否总是处于从属地位。我们编译了有关迁徙和居留同属物种的已发表的行为优势数据，收集了每个物种的体重和迁徙距离的额外数据。焦点物种包括来自世界各地的 28 个分类家族和 12 个目，种类繁多的鸟类。我们发现，迁徙物种通常处于从属地位，但这种关系在体型较大的物种中消失了。对于较小的鸟类（<500g），居留物种在 83%-88%的比较中表现出行为优势；对于较大的鸟类（>500g），居留物种在 25%-30%的比较中仅表现出行为优势。相对体重差异最好地预测了物种之间的优势关系，较大的物种在 80%-84%的比较中处于优势地位。然而，当迁徙和居留的体重相同时，居留物种在较小的鸟类中仍然更有可能处于优势地位，这表明其他因素也可能导致迁徙者处于从属地位。总的来说，我们的结果表明，在较小的物种中，迁徙的进化与较轻的体重和其他特征有关，这些特征削弱了迁徙者相对于居留者的竞争能力。相比之下，较大的物种似乎能够在不削弱其在攻击性竞争中的体型或竞争能力的情况下进化出迁徙能力，这表明在迁徙的进化上存在着依赖体型的限制。
