Annual variation in juvenile recruitment is an important component of duck population dynamics, yet little is known about the factors affecting the probability of surviving and breeding in the first year of life. Two hypothesized mechanisms to explain annual variability are indirect carry‐over effects (COEs) from conditions experienced during the prefledging period and direct effects from climatic conditions during the postfledging period. We used Cormack‐Jolly‐Seber models to estimate apparent survival and detection rates of 643 juvenile female lesser scaup (Aythya affinis) marked just prior to fledging at Red Rock Lakes National Wildlife Refuge in southwestern Montana, USA, 2010–2018. We evaluated COEs from hatch date, a hatch date × spring phenology interaction, and conspecific duckling density in addition to a direct climatic effect of winter conditions (indexed by the El Niño Southern Oscillation [ENSO]) and spring habitat conditions on the study area. We used growth data from a subset (n = 190) of known‐aged ducklings to estimate the influence of hatch date and conspecific density on prefledging growth to help identify mechanisms underlying COEs. Prefledging growth and juvenile apparent survival were negatively related to measures of conspecific duckling density. We found evidence that detection probability varied annually for juvenile (but not adult) scaup, possibly representing decisions to delay breeding and not return to or remain at the study site in their first year of life. Like with apparent survival, there was suggestive evidence that detection probability decreased with increasing duckling density in the previous year. Hatching date was weakly negatively related to detection probability, but unrelated to apparent survival, whereas neither vital rate was related to winter ENSO index. Our results are consistent with a process where density‐dependent growth rates in the prefledging period carry over to influence fitness in subsequent life‐cycle stages. If this pattern generalizes to other systems, this density COE may have important implications for our understanding of duck population dynamics and reaffirms the importance of maintaining abundant brood‐rearing habitats in conservation and management of ducks. © 2021 The Wildlife Society.

中文翻译：

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女性小斑纹的生长发育和招募

少年募集的年度变化是鸭种群动态的重要组成部分，但对影响生命第一年存活和繁殖可能性的因素知之甚少。两种解释年度变化的假想机制是前期阶段经历的间接结转效应（COE）和后期阶段气候条件的直接效应。我们使用Cormack-Jolly-Seber模型估算了643例未成年女性小腿ca（Aythya affinis）的表观存活率和检出率）标记为即将逃离美国西南部蒙大拿州的红岩湖国家野生动物保护区，2010-2018年。我们除了研究冬季条件（由厄尔尼诺南方涛动[ENSO]指数）和春季栖息地条件对研究区域的直接气候影响之外，还根据孵化日期，孵化日期×春季物候相互作用和同种鸭密度来评估COE。我们使用了子集（n = 190）的已知年龄的小鸭来估算孵化日期和同种密度对成熟生长的影响，以帮助确定COE的潜在机制。幼稚的生长和幼稚的表观存活率与同种小鸭密度的测量值呈负相关。我们发现证据表明，幼年（而不是成年）斑背鸡的检出概率每年都在变化，这可能代表了推迟繁殖的决定，而不是他们生命的第一年不返回或留在研究地点。与明显的存活一样，有暗示性的证据表明，前一年随着小鸭密度的增加，检测概率降低。孵化日期与检出概率之间呈弱负相关，但与表观存活率无关，而生命率与冬季ENSO指数均无关。我们的结果与一个过程相吻合，在该过程中，前期密度依赖的增长率继续影响着后续生命周期阶段的适应性。如果这种模式推广到其他系统，那么这种密度COE可能对我们对鸭子种群动态的理解具有重要意义，并重申在鸭子的保护和管理中保持丰富的育雏栖息地的重要性。©2021野生动物协会。