The role of group size and environmental factors on survival in a cooperatively breeding tropical passerine
The role of group size and environmental factors on survival in a cooperatively breeding tropical passerine
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DOI：
10.1111/j.1365-2656.2006.01155.x
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发表时间：
2006-11-01
影响因子：
4.8
通讯作者：
Komdeur, Jan
中科院分区：
文献类型：
--
作者：
Brouwer, Lyanne;Richardson, David S.;Komdeur, Jan
1.生存的差异是健康的一个主要决定因素，可能是由个人或环境特征引起的。此外，个体之间的相互作用可能通过密度依赖的负反馈效应影响生存。与温带地区的物种相比，我们对热带鸟类物种的种群过程和适合度变异知之甚少。为了研究种群大小或气候变量是否可以解释存活率的变化，我们使用捕获-再捕获模型，并结合来自领土合作繁殖的塞舌尔林莺(Acrocephalus Sechellensis)岛屿种群的长期数据集。缺乏迁出研究人群的迁移意味着我们的结果不会被分散所混淆。成人(84%)和青少年(61%)的年存活率都很高，性别之间没有差异。虽然不同年份间的存活率存在显著差异，但这种差异不能用总体种群数量或天气变量来解释。对于地区性物种，资源竞争将主要在当地范围内进行。因此，一个领土的面积和居住在该领土内的个人数量将比整体人口密度更适合衡量人口密度。因此，每个个体的领土质量指数(食物可获得性)和以群体规模衡量的当地密度都被包括在我们的分析中作为个体协变量。局部密度对生存有负面影响；生活在较大群体中的鸟类比生活在较小群体中的鸟类存活概率更低。食物的可获得性不影响生存。我们的研究表明，在一个区域物种中，尽管密度依赖效应可能无法在种群水平上检测到，但它们可以在个体区域水平上检测到--个体竞争的规模。这些结果将有助于更好地了解总体种群动态所涉及的小规模过程，特别是生活在相对稳定环境中的热带物种。
1. Variation in survival, a major determinant of fitness, may be caused by individual or environmental characteristics. Furthermore, interactions between individuals may influence survival through the negative feedback effects of density dependence. Compared to species in temperate regions, we have little knowledge about population processes and variation in fitness in tropical bird species.2. To investigate whether variation in survival could be explained by population size or climatic variables we used capture-recapture models in conjunction with a long-term data set from an island population of the territorial, cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). The lack of migration out of the study population means that our results are not confounded by dispersal.3. Annual survival was high, both for adults (84%) and juveniles (61%), and did not differ between the sexes. Although there was significant variation in survival between years, this variation could not be explained by overall population size or weather variables.4. For territorial species, resource competition will work mainly on a local scale. The size of a territory and number of individuals living in it will therefore be a more appropriate measure of density than overall population density. Consequently, both an index of territory quality per individual (food availability) and local density, measured as group size, were included as individual covariates in our analyses.5. Local density had a negative effect on survival; birds living in larger groups had lower survival probabilities than those living in small groups. Food availability did not affect survival.6. Our study shows that, in a territorial species, although density-dependent effects might not be detectable at the population level they can be detected at the individual territory level - the scale at which individuals compete. These results will help to provide a better understanding of the small-scale processes involved in the dynamics of a population in general, but in particular in tropical species living in relatively stable environments.