Behavioural and evolutionary ecology of avian brood parastism

禽类寄生的行为和进化生态学

• 批准号: 9556-2009
• 负责人: Sealy, Spencer
• 金额: $ 1.38万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2012
• 资助国家: 加拿大
• 起止时间: 2012-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=497518
• 关键词: Behavioural; evolutionary; ecology; avian; brood

Obligate brood parasites lay their eggs in nests of other species of birds, thus depending on the hosts to rear their offspring. As most hosts produce fewer young, adaptations for successful parasitism are countered by increasingly sophisticated adaptations by hosts that minimize the effects of parasitism or the likelihood that it will occur. Focusing primarily on parasitic cowbirds in North America, with comparative work on cuckoos in the old world, we are studying this interaction from the standpoints of parasite and host. Once believed to parasitize any nests they happened upon, cowbirds are now known to use some hosts more than others; this is not surprising because cowbirds lay fewer eggs than previously believed. They seem to select only certain hosts, perhaps the best ones. Studying cowbirds and hosts in different habitats, we are exploring the idea that selective host use increases a cowbird's reproductive success. With experiments, we are identifying attributes of hosts that may cause cowbirds to lay non-randomly: (1) nest defense and acquisition of requisite behaviour, (2) nest placement, (3) tolerance of parasitism, and (4) host quality. We are comparing differences within and among species that influence host use, such as size, aggressiveness at nests, parasitism of already-parasitized nests (and its conservation implications), egg-discrimination capabilities, and costs of acceptance versus rejection of cowbird eggs. We will focus mainly on host tolerance and host quality, building in part on our discovery 15 years ago of a small species that ejects cowbird eggs. Experiments will extend work on limits of how hosts see cowbird eggs and their own eggs relative to their abilities to recognize foreign eggs, and on bill-size constraints, answering the pervasive question of why so many host species tolerate costly parasitism. Knowing the minimum physical requirements for ejection and host-specific costs of acceptance is essential for understanding whether equilibrium or lag better explains acceptance in each host species. Rejection costs may explain acceptance in some hosts (equilibrium), whereas lag explains it in hosts that cannot recognize cowbird eggs.

专性孵化寄生虫在其他鸟类的巢中产卵，因此依赖宿主来抚养后代。由于大多数寄主产生的幼虫较少，因此寄主对成功寄生的适应被越来越复杂的适应所抵消，这些适应将寄生的影响或发生的可能性降至最低。我们主要关注北美的寄生牛鸟，与旧世界的杜鹃进行比较，从寄生虫和宿主的角度研究这种相互作用。曾经被认为寄生在它们碰巧发现的任何巢中的牛鸟，现在已知比其他人更多地利用一些宿主；这并不令人惊讶，因为牛鸟下的蛋比以前认为的要少。他们似乎只选择特定的东道主，也许是最好的。通过对不同栖息地的牛鸟和寄主的研究，我们正在探索选择性使用寄主可以增加牛鸟繁殖成功的想法。通过实验，我们确定了可能导致牛鸟非随机产卵的宿主属性：(1)巢防御和必要行为的获得，(2)巢的放置，(3)对寄生的容忍，以及(4)宿主质量。我们正在比较影响寄主使用的物种内部和物种之间的差异，例如大小、巢的侵略性、已经寄生的巢的寄生(及其保护影响)、卵识别能力以及接受和拒绝牛鸟蛋的成本。我们将主要关注宿主的耐受性和宿主质量，部分建立在我们15年前发现的一种排出牛鸟卵的小物种的基础上。实验将扩展关于宿主如何看待牛鸟蛋和它们自己的蛋相对于它们识别外来蛋的能力的限制，以及账单大小的限制，从而回答为什么如此多的宿主物种容忍代价高昂的寄生这个普遍存在的问题。了解排出的最低物理要求和特定于寄主的接受成本，对于理解平衡或滞后更好地解释每个寄主物种的接受是至关重要的。排斥成本可能解释了一些宿主的接受(均衡)，而滞后解释了不能识别牛鸟卵的宿主的接受。