Novel questions about avian nesting ecology

掠食者使在巢中的鸟类处于极端危险的境地，无论是作为蛋、雏鸟还是父母。例如，一项主要综述报道，23.1-87.0%的雀形目鸟类的巢产生了雏鸟，20.2-85.3%的巢失败是由于捕食者。因此，降低捕食风险的筑巢地点和行为对鸟类的繁殖策略至关重要，特别是在许多个体无法存活到第一个繁殖季节的物种中。巢穴隐藏通常在巢穴捕食研究中被评估。然而，巢穴气味的隐藏几乎没有被考虑过。这是令人惊讶的，因为雀形鸟巢穴最常见的捕食者是爬行动物和哺乳动物，它们更依赖嗅觉而不是视觉来寻找巢穴。同样，很少有人关注捕食者是如何利用气味来寻找鸟巢的。这些和许多其他被忽视的问题补充了我正在进行的研究项目，即评估隐密对树燕繁殖成功的重要性。为了量化它们的相对重要性，我将收集巢穴的视觉、听觉和嗅觉隐藏的数据；我在这里着重讨论后者。成虫、雏鸟和巢材产生的气味几乎没有被量化过。从筑巢到羽化后，我将使用最先进的设备：气相色谱-质谱法来量化树燕巢穴内容物的气味。一个长期的目标是收集来自众多物种的数据，以评估巢穴气味的生态特征（例如，洞穴与露天筑巢，地面与地上筑巢）和系统发育特征（例如，雀形目与非雀形目）。一旦我确定了产生巢穴气味的单分子（气味剂），下一步将是评估捕食者对哪些气味剂有反应。例如，候选气味将被输送到y形管中，模型捕食者（例如鹿鼠）可以选择访问控制与已知巢穴气味。后续工作将评估气味剂的组合。不同的捕食者物种（例如，老鼠和松鼠）喜欢不同的气味吗？在我每年监测的巢穴中，特定的气味是否与巢穴捕食率有关？我的研究是高度协作的；我和燕子生物学家（Golondrinas de las Americas）一起工作，他们已经发表了8篇论文，在前所未有的空间尺度上（即从火地岛到阿拉斯加）调查了燕子生物学的许多方面的空间变化。我的学生和我也将能够利用这个网络来探索巢穴气味的空间变化。我对这个新颖的研究项目中问题的多样性以及它给我的学生带来的机会感到兴奋。

Predators put birds at extreme risk while at nests, whether as eggs, nestlings, or parents. For example, one major review reported that 23.1-87.0% of passerine nests produced fledglings, and that 20.2-85.3% of nest failures were due to predators. Thus, nest sites and behaviours that reduce predation risk can be of pivotal importance to a bird's reproductive strategy, particularly in species where many individuals do not survive beyond their first breeding season. Nest concealment is commonly assessed in studies of nest predation. However, concealment of nest odours has scarcely been considered. This is surprising given that the most common predators of passerine nests are reptiles and mammals that rely more on olfaction than vision to find nests. Similarly, little attention has been devoted to considering how predators use odours to find bird nests. These and many other overlooked questions complement my ongoing research program that is evaluating the importance of crypsis to reproductive success in tree swallows. To quantify their relative importance, I will collect data on visual, acoustic, and olfactory concealment of nests; I focus here on the latter. Odours produced by adults, nestlings, and nest materials have scarcely been quantified for any species. From nest-building through to post-fledging, I will quantify odours of tree swallow nest contents using state-of-the-art equipment: gas chromatography-mass spectrometry. A longer term goal is to collect data from numerous species to evaluate ecological (e.g., cavity- versus open-nesting, ground- vs. above-ground nesting) and phylogenetic (e.g., passerine versus non-passerine) signatures in nest odours. Once I identify single-molecule (odorant) contributors to nest odours, a next step will be to evaluate odorants to which predators respond. For example, candidate odorants will be piped into Y-tubes where model predators (e.g., deer mice) can choose to visit control versus known nest odorants. Subsequent work will evaluate combinations of odorants. Do different predator species (e.g., mice versus squirrels) prefer different odorants? At nests I monitor each year, are particular odorants associated with rates of nest predation? My research is highly collaborative; I work with swallow biologists (Golondrinas de las Americas) that have already published 8 papers investigating spatial variation in numerous aspects of swallow biology at an unprecedented spatial scale (i.e., from Tierra del Fuego to Alaska). My students and I will similarly be able to tap into this network to explore spatial variation in nest odours. I am excited about the diversity of questions within this novel research program, and the opportunities it presents to my students.