Although population studies have long assumed that all individuals of a given sex and age are identical, ignoring among‐individual differences may strongly bias our perception of eco‐evolutionary processes. Individual heterogeneity, often referred to as individual quality, has received increasing research attention in the last decades. However, there are still substantial gaps in our current knowledge. For example, there is little information on how individual heterogeneity influences various life‐history traits simultaneously, and studies describing individual heterogeneity in wild populations are generally not able to jointly identify possible sources of this variation. Here, based on a mark–recapture data set of 9,685 known‐aged Wandering Albatrosses (Diomedea exulans), we investigated the existence of individual quality over the entire life cycle of this species, from early life to senescence. Using finite mixture models, we investigated the expression of individual heterogeneity in various demographic traits, and examined the origin of these among‐individual differences by considering the natal environmental conditions. We found that some individuals consistently outperformed others during most of their life. In old age, however, the senescence rate was stronger in males that showed high demographic performance at younger ages. Variation in individual quality seemed strongly affected by extrinsic factors experienced during the ontogenetic period. We found that individuals born in years with high population density tended to have lower performances during their lifespan, suggesting delayed density dependence effects through individual quality. Our study showed that among‐individual differences could be important in structuring individual life history trajectories, with substantial consequences at higher ecological levels such as population dynamics.

中文翻译：

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从早期到衰老：长寿海鸟的个体异质性。

尽管人口研究长期以来一直假设给定性别和年龄的所有个体都是相同的，但忽略个体差异可能会强烈偏重我们对生态进化过程的认识。在过去的几十年中，个体异质性（通常称为个体质量）已受到越来越多的研究关注。但是，我们目前的知识仍然存在很大差距。例如，关于个体异质性如何同时影响各种生活史特征的信息很少，描述野生种群中个体异质性的研究通常不能共同确定这种变异的可能来源。在此，根据9685个已知年龄的流浪信天翁（Diomedea exulans），我们调查了该物种从早期到衰老的整个生命周期中个体品质的存在。使用有限混合模型，我们研究了各种人口统计学特征中个体异质性的表达，并通过考虑出生时的环境条件来检验这些个体差异的起源。我们发现有些人一生中的表现始终优于其他人。然而，到了老年，男性的衰老率更高，而年轻人的人口统计学表现较高。个体质量的变化似乎受到个体发育期间经历的外部因素的强烈影响。我们发现，人口密度高的年份出生的人一生中的表现往往较低，表明通过个体质量延迟密度依赖性效应。我们的研究表明，个体差异对于构建个人生活史轨迹可能很重要，会对更高的生态水平（例如人口动态）产生重大影响。