Data from: Fecundity selection on ornamental plumage colour differs between ages and sexes and varies over small spatial scales

Avian plumage colours are some of the most conspicuous sexual ornaments, and yet standardized selection gradients for plumage colour have rarely been quantified. We examined patterns of fecundity selection on plumage colour in blue tits (Cyanistes caeruleus L.). When not accounting for environmental heterogeneity, we detected relatively few cases of selection. We found significant disruptive selection on adult male crown colour and yearling female chest colour and marginally nonsignificant positive linear selection on adult female crown colour. We discovered no new significant selection gradients with canonical rotation of the matrix of nonlinear selection. Next, using a long-term data set, we identified territory-level environmental variables that predicted fecundity to determine whether these variables influenced patterns of plumage selection. The first of these variables, the density of oaks within 50 m of the nest, influenced selection gradients only for yearling males. The second variable, an inverse function of nesting density, interacted with a subset of plumage selection gradients for yearling males and adult females, although the strength and direction of selection did not vary predictably with population density across these analyses. Overall, fecundity selection on plumage colour in blue tits appeared rare and inconsistent among sexes and age classes.鸟类羽色是最为醒目的性装饰特征之一，但针对羽色的标准化选择梯度却鲜有量化研究。本研究以蓝山雀（Cyanistes caeruleus L.）为研究对象，探究其羽色相关的繁殖选择模式。未考虑环境异质性时，本研究仅检测到少量选择案例：成年雄性头顶羽色存在显著的分裂选择，一岁龄雌性胸部羽色亦存在显著分裂选择；成年雌性头顶羽色则呈现边际不显著的正向线性选择。通过对非线性选择矩阵进行典范旋转分析后，未发现新的显著选择梯度。随后，本研究借助长期数据集，筛选出可预测繁殖成功率的领地尺度环境变量，以探究这些变量是否会对羽色选择模式产生影响。首个变量为巢址周边50米范围内的橡树密度，该变量仅对一岁龄雄性的选择梯度产生影响。第二个变量为筑巢密度的反比函数，该变量与一岁龄雄性及成年雌性的部分羽色选择梯度存在交互效应，但在本系列分析中，选择强度与方向并未随种群密度呈现可预测的变化。总体而言，蓝山雀羽色相关的繁殖选择较为罕见，且在不同性别与年龄组间表现出不一致性。