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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.

大多数生物生活在变化的环境中，质量好的和质量差的斑块点缀其间。大多数生物在其生命的某个阶段也会分散：通常主要的分散事件发生在动物出生和定居并开始繁殖之间。传统上，我们认为分散是一个抵消种群之间和种群内部差异进化的过程。当个体在栖息地周围移动时，它们会在每一代中有效地重新洗牌种群的特征。然而，环境的变化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。如果赢得这场竞争的能力是由个体的特征（例如，它的大小或出生时间）预测的，那么分散实际上可能是种群之间或种群内部差异的原因。这种非随机分散实际上可以对个体进行排序，而不是重新洗牌。最近在牛津附近对一种常见的英国鸟类——大山雀进行的研究表明，这正是正在发生的事情。随着时间的推移，种群中较大的个体倾向于在质量较好的生境中积累，而较小的个体倾向于在较差的生境中积累。这在一个连续的种群中产生了不同部分的鸟类大小的进化变化。这项工作的目的，是测试这个想法的各个组成部分，即扩散可以是一个非随机的过程，这取决于相关个体的特征，而这种非随机性取决于环境的变化程度。我们将研究牛津附近的一个大山雀种群，这个种群从1947年就开始研究了，我们已经获得了大量关于环境质量和个体分散方式的信息（例如，从它们的出生地到最终的繁殖地，我们已经追踪了4000多只雏鸟）。然而，尽管有丰富的数据，我们对散布的实际过程知之甚少，就个体如何利用它们的出生地和繁殖地之间的空间而言。我们的第一个目标是收集分散的数据，使用一个新的自动化跟踪系统，当鸟类访问林地周围的人工喂食点时，我们会对它们进行登记和识别。我们的第二个目标是更好地了解决定不同繁殖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，以及筑巢地点附近橡树的叶片发育时间；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来源是以橡树叶为食的毛毛虫。我们的第三个目标是进行一项实验，操纵环境质量，看看这是如何影响在那里定居和繁殖的鸟类的特征的。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，如果提供大量的巢址（箱），大山雀会以人为的高密度定居。由于对资源的竞争，鸟类在高密度环境下繁殖不太成功，这意味着这些地点的吸引力应该不如种群密度低时（即筑巢地点供应不足时）。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个体定居的地点的质量。要做到这一点，最简单的办法就是在一对鸟巢之间移动几只幼鸟：相比那些在大巢中长大的鸟，在小巢中长大的鸟生长得更好，因此应该更具竞争力，能够分散到更好的地方。