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（dispersal）与生境选择（habitat selection）行为，是生态学、进化生物学与保护生物学领域诸多核心问题的关键所在。幼体所经历的出生环境（natal environment），常被假说为影响扩散个体（dispersers）生境选择的重要因素之一；尽管如此，关于出生环境对野生脊椎动物扩散过程产生影响的实证证据仍较为匮乏。本研究依托一项覆盖濒危鸟类——蜗牛鸢（Rostrhamus sociabilis）整个北美分布范围、跨度达18年的筑巢与标记重捕（mark–resight）数据集，检验了扩散个体的出生环境效应（natal effects）对其繁殖位点选择（breeding-site selection）的影响，及其对繁殖成功率（reproductive success）与种群结构的调控效应。研究结果显示，无论扩散距离如何，扩散的蜗牛鸢更倾向于在与其出生湿地生境类型一致的湿地中筑巢——此类生境分为湖泊型（lacustrine）与草本沼泽型（palustrine）两类，但这一偏好会随个体年龄增长，以及在干旱时期出生而逐渐减弱。尤为关键的是，与选择非出生类型生境进行繁殖的个体相比，在出生类型相似生境中繁殖的扩散鸢，其巢成功率（nest success）与繁殖生产力（productivity）均更低。这些行为模式有助于解释该物种分布范围内近年被揭示的种群连通性（population connectivity）与空间结构特征，并证实存在选型繁殖（assortative breeding）现象：即个体更倾向与出生栖息地类型相同的同类进行交配繁殖。综上，即使在活动能力极强的动物类群中，出生环境仍可对自然种群产生长期且大范围的深远影响。