Ecologie Systematique Evolution, CNRS, AgroParisTech, Université Paris-Saclay, Orsay Cedex, France.
Departamento de Zoología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
J Anim Ecol. 2018 Nov;87(6):1738-1748. doi: 10.1111/1365-2656.12896. Epub 2018 Sep 10.
Coexistence between great tits Parus major and blue tits Cyanistes caeruleus, but also other hole-nesting taxa, constitutes a classic example of species co-occurrence resulting in potential interference and exploitation competition for food and for breeding and roosting sites. However, the spatial and temporal variations in coexistence and its consequences for competition remain poorly understood. We used an extensive database on reproduction in nest boxes by great and blue tits based on 87 study plots across Europe and Northern Africa during 1957-2012 for a total of 19,075 great tit and 16,729 blue tit clutches to assess correlative evidence for a relationship between laying date and clutch size, respectively, and density consistent with effects of intraspecific and interspecific competition. In an initial set of analyses, we statistically controlled for a suite of site-specific variables. We found evidence for an effect of intraspecific competition on blue tit laying date (later laying at higher density) and clutch size (smaller clutch size at higher density), but no evidence of significant effects of intraspecific competition in great tits, nor effects of interspecific competition for either species. To further control for site-specific variation caused by a range of potentially confounding variables, we compared means and variances in laying date and clutch size of great and blue tits among three categories of difference in density between the two species. We exploited the fact that means and variances are generally positively correlated. If interspecific competition occurs, we predicted a reduction in mean and an increase in variance in clutch size in great tit and blue tit when density of heterospecifics is higher than the density of conspecifics, and for intraspecific competition, this reduction would occur when density of conspecifics is higher than the density of heterospecifics. Such comparisons of temporal patterns of means and variances revealed evidence, for both species, consistent with intraspecific competition and to a smaller extent with interspecific competition. These findings suggest that competition associated with reproductive behaviour between blue and great tits is widespread, but also varies across large spatial and temporal scales.
大山雀 Parus major 和蓝山雀 Cyanistes caeruleus 的共存，以及其他洞巢物种，构成了物种共存的经典范例，导致了食物和繁殖、栖息场所的潜在干扰和竞争。然而，共存的时空变化及其对竞争的影响仍知之甚少。我们利用了一个基于 1957-2012 年欧洲和北非 87 个研究点的大山雀和蓝山雀巢箱繁殖的广泛数据库，共有 19075 只大山雀和 16729 只蓝山雀的巢，分别评估了产卵日期和巢卵数之间的相关性证据，以及与种内和种间竞争效应一致的密度。在最初的一组分析中，我们对一系列特定于地点的变量进行了统计控制。我们发现种内竞争对蓝山雀产卵日期（密度较高时产卵较晚）和巢卵数（密度较高时巢卵数较小）有影响，但在大山雀中没有发现种内竞争的显著影响，也没有发现两种物种之间的种间竞争的影响。为了进一步控制由一系列潜在混杂变量引起的特定于地点的变化，我们比较了两种物种之间密度差异的三个类别中大山雀和蓝山雀产卵日期和巢卵数的平均值和方差。我们利用了这样一个事实，即平均值和方差通常是正相关的。如果发生种间竞争，当异种种群的密度高于同种种群的密度时，我们预测大山雀和蓝山雀的巢卵数平均值会降低，方差会增加；而当同种种群的密度高于异种种群的密度时，这种减少就会发生。这种对平均值和方差的时间模式的比较，为这两种物种都提供了证据，表明存在种内竞争，在较小程度上也存在种间竞争。这些发现表明，蓝山雀和大山雀之间繁殖行为相关的竞争是普遍存在的，但也在大的时空尺度上发生变化。
