Density‐dependence effects acting on fecundity can be explained by two competing hypotheses. The individual adjustment hypothesis (IAH) states that, as population density increases, interference among individuals negatively affects their breeding performance. The second hypothesis, the habitat heterogeneity hypothesis (HHH), proposes that, as more individuals occupy the space available, lower quality habitats are increasingly used, causing average population fecundity to decline. In territorial species, it is often predicted that interference mechanisms (IAH) should be of less importance than spatial heterogeneity (HHH). Here, we test this prediction in Golden Eagles, using 35 years of reproduction monitoring data from a population that has been recolonizing the grounds of a French National Park (Ecrins) in the Alps. During the study period, the Eagle population increased from c. 11 to 41 territorial pairs, providing a good opportunity to explicitly assess fecundity across a gradient of densities. Under the IAH, we expect the fecundity of all territories to diminish as density rises. Under strict HHH, older territories should maintain higher fecundity across time, and a positive relationship between fecundity and the seniority of a territory should be observed. A density‐dependent pattern was clearly detected at the population level. At the territory level, the decrease of fecundity was strongly related to population size but not to territory seniority. Fecundity decreased similarly in all territories, suggesting that the IAH better explains the observed pattern. Two alternative mechanisms, related to the IAH, could be at play in this population: (1) negative interference by neighbours and non‐territorial Eagles and (2) the contraction of individual territories over time. Our results provide new insights into density dependence in territorial raptors, suggesting that, in addition to habitat heterogeneity, interference mechanisms might actually also play an important role.

中文翻译：

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个体调整比地区异质性更好地解释了金鹰天鹰座繁殖力的密度依赖性

密度依赖性对生育力的影响可以用两个相互矛盾的假设来解释。个体调节假设（IAH）指出，随着种群密度的增加，个体间的干扰会对他们的繁殖表现产生负面影响。第二个假设是栖息地异质性假设（HHH），它提出，随着更多的人占据可用空间，越来越多地使用质量较低的栖息地，导致平均人口繁殖力下降。在领土物种中，通常会预测干扰机制（IAH）的重要性应小于空间异质性（HHH）。在这里，我们使用来自35岁人口的繁殖监测数据检验了金鹰的这一预测，该种群已经重新定居了阿尔卑斯山的法国国家公园（Ecrins）。在学习期间C。11至41个领土对，这提供了一个很好的机会来明确评估密度梯度上的繁殖力。根据IAH，我们预计随着密度的提高，所有领土的生育力都会减少。在严格的HHH模式下，较旧的领土应在一段时间内保持较高的生育力，并且应观察到生育力与领土资历之间存在正相关关系。在人口水平上清楚地发现了密度依赖性模式。在领土一级，生育力的下降与人口规模密切相关，但与领土资历无关。在所有地区，生殖力都以类似的方式下降，这表明IAH可以更好地解释观察到的模式。与IAH相关的两种替代机制可能在该人群中起作用：（1）邻居和非领土老鹰的负面干扰，以及（2）随着时间的推移，各个领土的收缩。我们的结果提供了对领土猛禽密度依赖性的新见解，表明除了栖息地异质性之外，干扰机制实际上也可能起着重要作用。