Data from: Males migrate farther than females in a differential migrant: an examination of the fasting endurance hypothesis

Patterns of migration including connectivity between breeding and non-breeding populations and intraspecific variation in the distance travelled are important to study because they can affect individual fitness and population dynamics. Using data from 182 band recoveries across North America and 17 light-level geolocators, we examined the migration patterns of the northern flicker (Colaptes auratus), a migratory woodpecker. This species is unusual among birds because males invest more in parental care than females. Breeding latitude was positively correlated to migration distance because populations in the north appeared to travel farther distances than southern populations to find wintering locations with little snow cover. Connectivity was strong for populations west and east of the Continental Divide. Contrary to the three main hypotheses for intraspecific variation in migration distance, females wintered, on average, farther north than males, although there was overlap throughout their non-breeding range. This pattern contradicts those found in all other species found to date and is most consistent with the fasting endurance hypothesis if investment in parental care depletes the energy reserves of male flickers more than females. We thus propose a new factor, parental effort, which may influence optimal wintering areas and migration strategies within birds, and encourage future experimental studies to test the relationship between parental care roles and migration strategies of the sexes.

迁徙模式，包括繁殖种群与非繁殖种群间的连通性以及种内迁徙距离变异，具有重要研究价值，因其可影响个体适合度与种群动态。本研究依托北美地区182条环志回收数据与17台光感地理定位器（light-level geolocators）数据，对迁徙性鸟类北扑翅鴷（Colaptes auratus）的迁徙模式展开分析。该鸟类存在不同寻常的育幼投入模式：雄性相较于雌性投入更多育幼资源。繁殖纬度与迁徙距离呈显著正相关：北部种群为找到积雪较少的越冬地，需比南部种群迁徙更远的距离。大陆分水岭（Continental Divide）东西两侧的种群间连通性较强。尽管雌雄个体的非繁殖分布区存在重叠，但雌性的平均越冬纬度高于雄性，这一结果与迁徙距离种内变异的三大主流假说相悖。该模式与迄今已报道的所有鸟类迁徙模式均相悖；若雄性育幼投入比雌性更多地消耗其能量储备，则该模式与禁食耐力假说（fasting endurance hypothesis）最为契合。据此，我们提出一个新的影响鸟类最优越冬区与迁徙策略的因素：育幼投入（parental effort），并呼吁未来开展实验研究，以验证育幼角色差异与两性迁徙策略之间的关联。