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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.

大多数生物体生活在多种多样的环境中，质量好的和质量差的斑块错落有致。大多数生物在其生命的某个阶段也会扩散：通常主要的扩散事件发生在动物出生和定居并开始繁殖之间。传统上，我们认为扩散是一个过程，它抵消了种群之间和种群内部差异的演变。当个体在其栖息地周围移动时，它们在每一连续的世代中有效地重新洗牌种群的特征。然而，环境的不同意味着一些地方比其他地方更适合定居，在这些地方定居应该有竞争。如果通过个体的特征(例如，个体的大小或出生时间)来预测赢得这场比赛的能力，那么分散实际上可能是群体之间或群体内部差异的原因。这种非随机扩散实际上可以对个体进行排序，而不是对种群进行重新洗牌。最近在牛津附近研究的一种常见的英国鸟类--大山雀--的一些研究表明，这正是正在发生的事情。随着时间的推移，种群中较大的个体往往会在质量较好的生境中积累，而较小的个体往往会在较差的生境中积累。这导致了单个连续种群中不同部分鸟类的大小发生了进化变化。这项工作的目的是检验扩散可以是一个非随机过程的想法的各个组成部分，这取决于有关个人的特征，以及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个大山雀种群，这个种群自1947年以来一直被研究，关于环境质量和个体分散的方式已经有了大量的信息(例如，超过4000只个体雏鸟从它们的出生地被跟踪到它们最终的繁殖地点)。然而，尽管有丰富的数据，就个体如何利用出生地和繁殖地之间的空间而言，我们对扩散所涉及的实际过程知之甚少。我们的第一个目标将是使用一种新的自动化跟踪系统收集扩散数据，当鸟类访问林地周围的人工喂食点时，可以在该系统中进行登记和识别。我们的第二个目标是更好地了解决定不同鸟类繁育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，以及靠近筑巢地点的橡树叶发育的时间；初步数据表明，橡树是这些鸟类非常重要的资源，可能是因为它们后代的主要食物供应是以橡树叶为食的毛虫。我们的第三个目标是进行一项操纵环境质量的实验，看看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密度的潜在筑巢地点来做到这一点。我们知道，如果提供大量的筑巢地点(箱)，大山雀将以人为的高密度定居。由于对资源的竞争，这些鸟在高密度下繁殖不太成功，这意味着这些地点应该比种群低密度时，即筑巢地点供不应求的时候更不具吸引力。最后，我们将对个体鸟类的特征进行操纵，以测试这如何影响这些个体栖息地的质量。要做到这一点，最容易的方法是在两对巢之间移动几只幼鸟：与那些在大窝中长大的鸟相比，在小窝中饲养的鸟生长得更好，因此应该更具竞争力，而且能够分散到更好的地点。