Sandvig Erik M, Coulson Tim, Kikkawa Jiro, Clegg Sonya M
Department of Zoology, University of Oxford, Oxford, United Kingdom.
Edward Grey Institute for Field Ornithology, Department of Zoology, University of Oxford, Oxford, United Kingdom.
PLoS One. 2017 Apr 28;12(4):e0176360. doi: 10.1371/journal.pone.0176360. eCollection 2017.
Understanding the influence of environmental factors on population dynamics is fundamental to many areas in biology. Survival is a key factor of population biology, as it is thought to be the predominant driver of growth in long-lived passerines, which can be influenced by both biotic and abiotic environmental conditions. We used mark-recapture methods and generalized linear mixed models to test the influence of density and climatic variation, measured at a regional and local scale (Southern Oscillation Index [SOI] and rainfall, respectively), on seasonal variation in survival rates of an insular population of Silvereyes (Zosterops lateralis chlorocephalus), during a 15-year study period, off the east coast of Australia. We found overall high survival rates for adults and juveniles (81% and 59%, respectively). Local scale climate (i.e. rainfall) and density were the principal environmental factors influencing their survival, both with a negative relationship. A significant interactive effect of density and rainfall influenced survival as they both increased. However, survival remained low when density was at it highest, independent of the amount of rainfall. Nestling survival was negatively influenced by rainfall and density, positively by SOI, and chicks that hatched later in the breeding season had higher survival rates. The regional scale climate variable (i.e. SOI) did not explain survival rates as strongly as rainfall in any age class. Our results contribute to the understanding of insular avian population dynamics and the differential effects of environmental factors across age classes. Climatic predictions expect El Niño events to increase, meaning dryer conditions in eastern Australia, potentially increasing Silvereye survival across age classes. However, the long-term effect of lower rainfall on food availability is unknown; consequently, the outcome of lower rainfall on Silvereye survival rates is uncertain.
了解环境因素对种群动态的影响是生物学许多领域的基础。生存是种群生物学的关键因素，因为它被认为是长寿雀形目鸟类种群增长的主要驱动因素，而这可能受到生物和非生物环境条件的影响。在一项为期15年的研究中，我们利用标记重捕法和广义线性混合模型，测试了在区域和局部尺度（分别为南方涛动指数[SOI]和降雨量）上测量的密度和气候变化对澳大利亚东海岸外一个银眼鸟（Zosterops lateralis chlorocephalus）岛屿种群生存率季节变化的影响。我们发现成年鸟和幼鸟的总体生存率较高（分别为81%和59%）。局部尺度的气候（即降雨量）和密度是影响它们生存的主要环境因素，二者均呈负相关。密度和降雨量之间存在显著的交互作用，随着它们的增加都会影响生存率。然而，当密度处于最高水平时，生存率仍然很低，与降雨量无关。雏鸟的生存受到降雨量和密度的负面影响，受到SOI的正面影响，并且在繁殖季节后期孵化的雏鸟生存率更高。区域尺度的气候变量（即SOI）在任何年龄组中对生存率的解释都不如降雨量有力。我们的研究结果有助于理解岛屿鸟类的种群动态以及环境因素对不同年龄组产生的不同影响。气候预测预计厄尔尼诺事件将会增加，这意味着澳大利亚东部的气候会更加干燥，这可能会提高银眼鸟各年龄组的生存率。然而，降雨量减少对食物供应的长期影响尚不清楚；因此，降雨量减少对银眼鸟生存率的影响结果也不确定。
