Fitness Consequences of Avian Coloniality

这个项目试图理解为什么动物群居。许多不同的生物，包括人类，表现出不同程度的群体生活：一些动物生活在小群体中或单独生活，而同一种群的其他动物可能生活在巨大的群体中。要理解为什么有些人喜欢生活在大群体中，而另一些人喜欢生活在小群体中，需要了解这种选择的生殖后果。为什么某些动物从一种规模的群体中受益，而另一些动物显然从另一种规模的群体中受益？这个问题在这项研究中得到了解决，这项研究的重点是一种殖民地繁殖的鸟类，悬崖燕子（hirundo pyrrhonota_），它在北美西部大部分地区陡峭的悬崖和峡谷的侧面以及桥梁和建筑物的屋檐下繁殖。目的是确定不同的鸟类如何在不同大小的筑巢群中对自己进行分类，以及根据什么进行分类；是否存在一个对所有鸟类都最适合的群体大小（繁殖成功率最高）；燕子对特定大小的巢群的偏好是否基于基因，从而遗传自其父母；以及如果它们的筑巢群的大小发生变化，它们的筑巢成功率会受到怎样的影响。该研究主要使用了标记-再捕获方法，其中包括鸟类绑带：鸟类在特定地点被绑带，它们随后的活动和寿命取决于在该地点或以后的其他地点再次捕获它们。这项研究建立在过去15年对悬崖燕子种群的研究基础上。这个项目将进一步加深我们对为什么动物群体大小在自然界中有所不同的理解。群体规模影响动物行为的许多方面：例如，疾病的传播，对食物等资源的竞争程度，交配策略的类型，以及个体之间的合作和利他主义程度，都受到社会群体规模的严重影响。如果我们首先知道是什么原因导致群体规模不同，如果我们知道不同的群体是否由不同种类的个体组成，我们就能更好地理解群体生活的这些重要后果。崖燕提供了一个被充分研究的动物模型，它的社会行为与其他社会物种相似，它将使我们深入了解许多生物中控制群体形成的基本过程。

9613638 BROWN This project seeks to understand why animals live in groups. Many different organisms, including humans, show different degrees of group-living: some animals live in tiny groups or solitarily, whereas others in the same population may reside in enormous colonies. To understand why some individuals prefer living in large groups and others in small groups requires knowing the reproductive consequences of such choices. In what way do certain animals benefit from groups of one size while others apparently benefit from groups of another size? This question is addressed in this research, which focuses on a colonially breeding bird, the cliff swallow (_Hirundo pyrrhonota_), that breeds on the sides of steep cliffs and canyons and underneath the eaves of bridges and buildings throughout much of western North America. The objectives are to determine how different birds sort themselves among different sized nesting colonies and on what basis; whether there is a single colony size that is best for all birds (where reproductive success is greatest); whether a swallow's preference for a particular sized nesting colony is genetically based and thus inherited from its parents; and how the birds' nesting success is affected if their nesting colony is changed in size. The research uses primarily mark-recapture methods that involve bird banding: birds are banded at a particular site and their subsequent activity and lifespan is determined by recatching them at that site or others in later years. This study builds on 15 years of past work on this cliff swallow population. This project will further our understanding of why animal group sizes vary in nature. Group size affects many aspects of animal behavior: for example, the spread of disease, extent of competition for resources such as food, type of mating strategy, and extent of cooperation and altruism among individuals are all influenced heavily by the size of a social group. We can better understand these important conseque nces of group life if we know what causes groups to vary in size in the first place and if we know whether different groups are composed of different kinds of individuals. The cliff swallow provides a well-studied animal model whose social behavior parallels that of other social species, and it will yield insight into fundamental processes that govern group formation in many kinds of organisms.