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.

解析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领域诸多核心研究议题的关键所在。学界常假设，影响扩散个体栖息地选择的核心因素之一，是幼体时期经历的出生环境；然而，针对野生脊椎动物扩散个体的出生环境效应，现有研究证据仍较为有限。本研究基于覆盖濒危鸟类蜗牛鸢（Rostrhamus sociabilis）北美全境地理分布范围的18年巢址记录与标记重见（mark–resight）数据，检验了扩散个体的出生环境效应对其繁殖位点选择的影响，以及该效应对繁殖成功率与种群结构的连锁效应。扩散的蜗牛鸢更倾向于在与自身出生湿地生境类型一致（湖相（lacustrine）或沼相（palustrine））的湿地中筑巢，且该偏好不受扩散距离的影响，但会随个体年龄增长以及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选择其他生境繁殖的个体。上述行为模式有助于解释该物种地理分布范围内近期被报道的种群连通性与空间结构特征，同时揭示了同型繁殖（assortative breeding）现象的存在：即个体更倾向与出生湿地类型与自身出生生境一致的同类进行繁殖配对。由此可见，即便对于移动能力极强的动物而言，出生环境仍可对自然种群产生长期且大范围的影响。