Møller Anders Pape, Laursen Karsten
Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech Université Paris-Saclay Orsay Cedex France.
Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences Beijing Normal University Beijing China.
Ecol Evol. 2019 May 6;9(11):6559-6567. doi: 10.1002/ece3.5234. eCollection 2019 Jun.
Population size is generally limited by resource availability during and outside the breeding season. Therefore, maximum size of flocks may provide important information on population regulation and the influence of diet and trophic level on maximal degree of sociality. We hypothesized that (a) flock size should increase with nutrient availability; (b) flock size should decrease with latitude because productivity is higher at lower latitude; (c) aquatic habitats should have larger flocks than terrestrial habitats because the former are less accessible; (d) smaller species should have larger flocks because they require overall less food; (e) human-impacted species that live in perturbed habitats should have smaller flocks than other species; (f) flock size should decrease with increasing trophic level because there is a reduction in biomass due to conversion at each trophic level; and (g) flocks of species depending on ancestral landscapes should have decreased in size in recent years due to human impact (e.g., land-use). We obtained 1564 observations of flocks that exceeded 100,000 individuals in order to test the predictions listed above. Most effect sizes were small to medium accounting for 1%-9% of the variance, while large effects accounting for 25% or more were only found for total nitrogen used per km and area used for agriculture. Changes in large bird flocks were caused by habitat degradation and persecution, and temporal decline in size of large flocks revealed changes in nutrient use, reductions in nutrient cycling, and changes in flock size linked to trophic level.
种群规模通常受到繁殖季节内外资源可利用性的限制。因此，鸟群的最大规模可能为种群调节以及饮食和营养级对最大社交程度的影响提供重要信息。我们假设：(a) 鸟群规模应随养分可利用性增加；(b) 鸟群规模应随纬度降低，因为低纬度地区生产力更高；(c) 水生栖息地的鸟群规模应大于陆地栖息地，因为前者获取资源更难；(d) 体型较小的物种应具有更大的鸟群，因为它们总体所需食物较少；(e) 生活在受干扰栖息地的受人类影响物种的鸟群规模应小于其他物种；(f) 鸟群规模应随营养级升高而减小，因为每个营养级的转化都会导致生物量减少；(g) 依赖原始景观的物种的鸟群规模近年来应因人类影响（如土地利用）而减小。我们获取了超过100,000只个体的1564次鸟群观测数据，以检验上述预测。大多数效应量较小至中等，占方差的1%-9%，而占25%或更多的大效应仅在每千米总氮使用量和农业用地面积方面被发现。大型鸟群的变化是由栖息地退化和迫害导致的，大型鸟群规模的时间性下降揭示了养分利用的变化、养分循环的减少以及与营养级相关的鸟群规模变化。
