Using phenological drivers of demography in conservation

了解密度依赖的过程和影响其健身结果的条件是种群生态学的一个关键组成部分，但在野生种群的密度依赖性影响的机制很少被理解。大多数密度依赖过程的研究都集中在确定影响密度空间变化的条件。然而，在繁殖种群内的个体之间的物候变化也可能影响当地的密度依赖的强度，如果个人对这些过程的贡献随生殖周期的阶段而变化。因此，同步繁殖可能是当地种群内密度依赖过程的主要贡献者。确定生殖同步，密度依赖和人口之间的联系是特别重要的物种保护的关注，管理，以促进生殖同步和相关的健身效益可能是可能的。在欧洲的低地地区，涉禽的数量经历了严重和广泛的下降，并越来越局限于少数自然保护区。在欧盟共同农业政策范围内建立了供资机制，试图通过农业环境计划制止和扭转这种下降趋势，但尽管投入了大量资金，这些努力都失败了。因此，人们日益认识到，需要通过更深入地了解土地管理与物种数量之间的相互作用，确定行动目标。AES提供合适的繁殖栖息地，可以成功地吸引繁殖涉禽，但高水平的巢和小鸡捕食的通才捕食者（主要是红狐，狐）一贯防止人口恢复。地面筑巢涉禽天生容易受到捕食，许多物种已经发展出半殖民地繁殖和捕食者群体围攻等策略来抵消这些影响，但这些行为适应以前没有被考虑在AES的设计，和零碎的部署AES，支持非常小的人口实际上可能会加剧人口下降。捕食率涉禽巢和雏鸟一般较低时，筑巢密度高，但往往有很大的变化，在这些关系。反捕食行为的适应性的有效性可能会提高繁殖是同步的，因为防御行为往往通过繁殖周期加剧，但这些密度依赖过程的贡献生殖同步是未知的。高水平的捕食通常会导致繁殖的繁殖，因为捕食的巢穴在整个繁殖季节都会被替换。因此，捕食者的行为可能会降低反捕食者策略的有效性;这一循环可能会通过管理来打破，以促进生殖同步。为了检验繁殖同步性在推动生产力和种群增长中的作用，以及管理促进保护关注物种繁殖同步性的潜力，我们建议在繁殖涉禽中进行大规模的捕食者分布和繁殖同步性实验操作（北方麦鸡，Vanellus vanellus，和普通红脚鹬，Tringa totanus）种群在低地潮湿的草地上，并量化同步可以提高当地生产力的机制。这一信息将用于建立潜在人口增长率的模型，通过土地管理战略，将人口增长的环境和行为驱动因素结合起来，可以实现这一增长率。种群内的物候变化可能会影响密度依赖的过程中，在广泛的设置，并确定这些环节，因此，可以大大提高我们的理解，在人口生态学和保护管理的关键过程。

Understanding density-dependent processes and the conditions that influence their fitness consequences is a key component of population ecology, but the mechanisms determining density-dependent effects in wild populations are rarely understood. Most studies of density-dependent processes have focussed on identifying conditions influencing spatial variation in densities. However, phenological variation among individuals within breeding populations may also influence the strength of local density-dependence, if individual contributions to these processes vary with stage of the reproductive cycle. Synchronous breeding could thus be a major contributor to density-dependent processes within local populations. Identifying links between reproductive synchrony, density-dependence and demography is particularly important in species of conservation concern, for which management to facilitate reproductive synchrony and associated fitness benefits may be possible. In lowland areas of Europe, wading bird populations have undergone severe and widespread declines, and are increasingly restricted to small numbers of nature reserves. Funding mechanisms have been developed within the EU Common Agricultural Policy to attempt to halt and reverse these declines, through agri-environment schemes (AES), but these attempts have failed despite the very large sums of money involved. There is therefore growing recognition of the need to target actions through a much more profound understanding of the interactions between land management and species demography. AES that deliver suitable breeding habitat can successfully attract breeding waders, but high levels of nest and chick predation by generalist predators (primarily red foxes, Vulpes vulpes) consistently prevent population recovery. Ground-nesting waders are inherently vulnerable to predation, and many species have evolved strategies such as semi-colonial breeding and group mobbing of predators to counteract these impacts, but these behavioural adaptations have not previously been considered in the design of AES, and piecemeal deployment of AES that support very small populations may in fact be exacerbating the population declines. Predation rates on wader nests and chicks are generally lower when nesting densities are high, but there is often a great deal of variation in these relationships. The effectiveness of anti-predator behavioural adaptations may be enhanced when breeding is synchronous, as defence behaviour often intensifies through the breeding cycle, but the contribution of reproductive synchrony to these density-dependent processes is unknown. High levels of predation typically result in reproductive asynchrony, as predated nests are replaced throughout the breeding season. The actions of predators may therefore be reducing the effectiveness of anti-predator strategies; a cycle which can potentially be broken through management to facilitate reproductive synchrony. To test the role of reproductive synchrony in driving productivity and population growth, and the potential for management to facilitate reproductive synchrony in species of conservation concern, we propose to carry out a large-scale experimental manipulation of predator distribution and reproductive synchrony in breeding wading bird (northern lapwing, Vanellus vanellus, and common redshank, Tringa totanus) populations on lowland wet grasslands, and to quantify the mechanisms through which synchrony can enhance local productivity. This information will be used to model potential rates of population growth that could be achieved by land management strategies that integrate both environmental and behavioural drivers of population growth. Within-population phenological variation could influence density-dependent processes in a wide range of settings, and identifying these links may therefore substantially improve our understanding of key processes in population ecology and conservation management.