Data from: Affinity for natal environments by dispersers impacts reproduction and explains geographic structure of a highly mobile bird

Understanding dispersal and habitat selection behaviours is central to many problems in ecology, evolution and conservation. One factor often hypothesized to influence habitat selection by dispersers is the natal environment experienced by juveniles. Nonetheless, evidence for the effect of natal environment on dispersing, wild vertebrates remains limited. Using 18 years of nesting and mark–resight data across an entire North American geographical range of an endangered bird, the snail kite (Rostrhamus sociabilis), we tested for natal effects on breeding-site selection by dispersers and its consequences for reproductive success and population structure. Dispersing snail kites were more likely to nest in wetlands of the same habitat type (lacustrine or palustrine) as their natal wetland, independent of dispersal distance, but this preference declined with age and if individuals were born during droughts. Importantly, dispersing kites that bred in natal-like habitats had lower nest success and productivity than kites that did not. These behaviours help explain recently described population connectivity and spatial structure across their geographical range and reveal that assortative breeding is occurring, where birds are more likely to breed with individuals born in the same wetland type as their natal habitat. Natal environments can thus have long-term and large-scale effects on populations in nature, even in highly mobile animals.

探究扩散行为与栖息地选择机制，是生态学、进化生物学及保护生物学诸多核心研究议题的关键所在。此前学界常提出假说，认为幼体经历的出生环境（natal environment）会对扩散个体的栖息地选择产生影响。然而，目前关于出生环境对野生扩散脊椎动物产生影响的相关证据仍较为匮乏。
本研究以濒危鸟类蜗牛鸢（Rostrhamus sociabilis）为研究对象，收集了其北美全域分布范围内长达18年的筑巢与标记重捕（mark–resight）数据，以此检验扩散个体的繁殖位点选择是否受出生环境影响，并探究该效应对繁殖成功率与种群结构的作用。研究发现，扩散个体更倾向于在与自身出生湿地属于相同生境类型（湖沼型lacustrine或草本沼泽型palustrine）的湿地中筑巢，且该偏好不受扩散距离的影响；但这种偏好会随个体年龄增长，以及个体在干旱年份出生而减弱。值得注意的是，在与出生环境相似的生境中繁殖的扩散个体，其巢成功率与繁殖生产力均低于未选择此类生境的个体。此类行为有助于解释该物种分布范围内近期被报道的种群连通性与空间结构特征，同时揭示了选型交配（assortative breeding）现象的存在：即个体更倾向于与自身出生湿地类型相同的同类进行繁殖。由此可见，即便在活动性极强的动物类群中，出生环境仍能对自然种群产生长期且大范围的影响。