Habitat quality, individual variation and dispersal in the great tit: population consequences

大山雀的栖息地质量、个体差异和扩散：种群影响

基本信息

批准号：
NE/D011744/1
负责人：
Ben Sheldon
金额：
$ 41.48万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FD011744%2F1
关键词：
Habitat quality individual variation dispersal

项目摘要

Most organisms live in environments that vary, with good and poor quality patches interspersed. Most organisms also disperse at some stage in their lives: usually the major dispersal event comes between birth and when an animal settles and begins to reproduce. Traditionally, we think of dispersal as a process that counter-acts the evolution of differences between, and within, populations. As individuals move around their habitat, they effectively re-shuffle the characteristics of the population during each consecutive generation. However, the fact that the environment varies means that some places are better spaces to settle than others, and that there should be competition to settle in these places. If the ability to win this competition is predicted by an individual's characteristics (for example, its size, or time of birth), then dispersal can actually be the cause of differences between, or within, populations. Rather than re-shuffling populations, non-random dispersal of this kind can actually act to sort individuals. Some recent work on a common British bird, the great tit, studied near Oxford, suggests that this is exactly what is occurring. Over time, the larger individuals in the population tended to accumulate in the better quality habitats, whereas the smaller individuals tended to accumulate in the poorer habitats. This produced an evolutionary change in the sizes of the birds in different parts of a single continuous population. The aim of this work, is to test various components of the idea that dispersal can be a non-random process, depending on the characteristics of the individual concerned, and that this non-randomness depends on how variable the environment is. We will study a population of great tits near Oxford, that has been studied since 1947, and for which a great deal of information is already available regarding the quality of the environment, and the way that individuals disperse (for example, over 4000 individual nestlings have been tracked from their place of birth to their eventual breeding location). However, despite the wealth of data, we know remarkably little about the actual processes involved in dispersal, in terms of how individuals use space between their birth site and their breeding site. Our first aim will be to collect dispersal data, using a new, automated, tracking system, where birds are registered and identified as they visit artificial feeding sites placed around the woodland. Our second aim is to develop a better understanding of the key factors that determine the environmental quality of different sites for the breeding birds. We will focus particularly on the breeding density of individuals, and the timing of leaf development of oak trees near to nest sites; preliminary data suggest that oak trees are a very important resource for these birds, probably because the main food supply for their offspring is caterpillars that feed on oak leaves. Our third aim is to carry out an experiment that manipulates the quality of the environment, to see how this affects the characteristics of the birds that settle and breed there. We will do this by creating different densities of potential nest-sites. We know that great tits will settle at artificially high densities, if nest-sites (boxes) are provided in great abundance. The birds breed less successfully at high density because of competition for resources, meaning that these sites should be less attractive than when a population is at low density, i.e. when nest-sites are in short supply. Finally, we will carry out manipulations of the characteristics of individual birds, to test how this affects the quality of the sites these individuals settle in. This is most easily done by moving a few young between pairs of nests: the birds that are reared in reduced broods grow better and should therefore be more competitive, and able to disperse to better sites than those that have grown up in enlarged broods.

大多数生物都生活在各种环境中，质量良好和质量较差。大多数生物也分散在他们生活中的某个阶段：通常，主要的分散事件是在出生之间和动物定居并开始繁殖时的。传统上，我们认为散布是一个反应人群之间和内部差异演变的过程。当个人在栖息地周围移动时，他们在连续每一代中有效地重新削减了人口的特征。但是，环境变化的事实意味着某些地方比其他地方更好地定居空间，并且应该有在这些地方定居的竞争。如果通过个人的特征（例如，其大小或出生时间）预测赢得此竞赛的能力，那么分散实际上可能是人群之间或内部差异的原因。这种非随机散布与其重新置换人群，实际上可以对个人进行分类。最近在牛津附近研究的一只英国鸟类伟大的山雀的一些著作表明，这正是发生的事情。随着时间的流逝，人口中较大的人倾向于在质量更高的栖息地中积累，而较小的个体倾向于在贫穷的栖息地中积累。这导致了单个连续人群的不同部分的鸟类大小的进化变化。这项工作的目的是测试分散可以是非随机过程的想法的各种组成部分，具体取决于相关个人的特征，并且这种非随机性取决于环境的可变程度。我们将研究牛津附近的一群大山雀，自1947年以来就已经进行了研究，并为此提供了有关环境质量的大量信息以及个人分散的方式（例如，超过4000个单独的巢穴从他们的出生地到最终的繁殖地点进行了跟踪）。但是，尽管数据丰富，但对于个人如何在出生地和繁殖地点之间使用空间而言，我们对分散所涉及的实际过程知之甚少。我们的第一个目的是使用一种新的，自动化的跟踪系统收集分散数据，在该系统访问林地周围放置的人造喂养地点时，鸟类被注册并确定。我们的第二个目标是更好地了解决定繁殖鸟类不同地点环境质量的关键因素。我们将特别关注个体的繁殖密度，以及巢穴附近橡树的叶片开发时间；初步数据表明，橡树是这些鸟类的非常重要的资源，可能是因为其后代的主要食物供应是以橡木叶子为食的毛毛虫。我们的第三个目标是进行操纵环境质量的实验，以了解这如何影响在那里定居和繁殖的鸟类的特征。我们将通过创建不同的潜在巢穴密度来做到这一点。我们知道，如果大量提供巢穴（盒子），那么伟大的山雀将定居在人为的高密度上。由于资源的竞争，鸟类在高密度下繁殖的繁殖程度较低，这意味着这些地点的吸引力应比人口低密度（即巢穴供应量短时）时的吸引力不那么吸引力。最后，我们将对单个鸟类的特征进行操纵，以测试这如何影响这些人安顿下来的地点的质量。这是通过在两对巢之间移动几个年轻人来完成的：饲养的鸟减少的育雏效果更好，因此应该更有竞争力，并且能够比在育雏肿大的育雏成长的地方分散到更好的地点。