A new theory of clutch size evolution: Consequences of morphology at fledging on mobility and survival interacting with parental energy expenditure (FMR)

为了养育后代，父母应该付出多大的努力？这种努力如何影响父母试图养育的后代的数量和存活率？这些问题一个多世纪以来一直引起科学家的兴趣，并对野生动物的种群动态产生重大影响。这些问题在鸣禽中得到了强调，因为不同物种的父母试图抚养的幼鸟数量差异很大。即使在同一栖息地繁殖的物种之间，比如在亚利桑那州的高海拔河岸栖息地，物种在它们试图抚养的后代数量上也有很大的差异。例如，在该栖息地，一只绿尾土莺通常会产下3到4个蛋，一只红脸莺会产下4到5个蛋，而一只山雀可能会产下8个蛋。提出了一种新的理论来解释这种基于后代和父母死亡风险的差异，这笔拨款将资助对新理论的测试。不同物种的幼雏被捕食者吃掉的风险也不同，黄莺或莺的开放式杯状巢穴被捕食的风险很高，而山雀的洞状巢穴被捕食的风险很低。这些捕食风险的差异影响了幼鸟在巢中待的时间；像土莺和莺这样的物种在孵化后8到11天离开它们危险的巢穴，而山雀在孵化后20到22天才离开它们安全的洞穴巢穴。因此，雏鸟和莺离开巢穴时不能飞，而山雀离开巢穴时却能完全飞行。雏鸟离开巢穴时发育状态的差异也可能影响它们开始觅食的速度，山雀可能在离开巢穴后几天内觅食，而山雀可能需要3周才能发育出这种能力。与山雀相比，山雀的幼鸟几乎会立即开始获取一些自己的食物，并跟随父母减少旅行，因此父母必须更加努力地为每只幼鸟提供所有的食物。不同物种的父母愿意工作的程度不同，这取决于它们在一年的周期中死亡的风险。综上所述，这些影响可以解释为什么物种在试图抚养的幼崽数量上存在差异，并对物种的种群动态产生关键影响。拟议的工作将使用观察和实验的方法来检验这些假设。羽翼期（后代离开巢穴后）是人口统计学的关键时期，但生存的种间差异是未知的，文献将有助于理解种群对不断变化的环境条件的脆弱性。鉴于观鸟对社会的经济和美学重要性，这种保护知识很重要。本项目将培养3名研究生进行论文研究。每年，1名技术人员和6名本科生将接受现场技术和科学行为方面的培训，以及来自不同学科（生物学内外）的8名本科生，以转录父母行为的视频。后者提供外联，使不同的学生参与科学原理。学生将通过讨论来接受教育，这些讨论将用于教授正在进行的工作的科学原理。为了甄别可能的招募对象，我们会采用广泛的广告宣传方法，进一步增加我们可招募的社会和文化群体的多样性。最后，巢穴提供了丰富的视频资源，可以展示物种之间在社会互动中的差异，以及有趣的捕食事件视频。研究人员开始获取短的高清视频，制作一个关于父母和子女行为以及捕食事件的教育系列，并将其放在YouTube上向公众宣传。PBS自然频道正在拍摄一部关于鸟巢建筑和鸟类家庭生活的纪录片，其中将包括焦点现场的镜头，以进一步增加公众宣传。

How hard should parents work to raise offspring, and how does this work effort influence the number and survival of offspring that parents attempt to raise? These are questions that have intrigued scientists for more than a century, and have major implications for population dynamics of wild animals. These questions have been highlighted among songbirds because species vary extensively in the number of young that parents attempt to raise. Even among species that breed in the same habitat, such as high elevation riparian habitat in Arizona where work will be conducted, species vary extensively in the number of offspring they attempt to raise. For example, a green-tailed towhee in that habitat typically lays 3 or 4 eggs, a red-faced warbler lays 4 or 5 eggs, while a mountain chickadee may lay 8 eggs. A new theory to explain this variation based on risk of mortality to offspring and parents is proposed and this grant will fund tests of the new theory. Species differ in the risk of their young being eaten by predators, with the open cup nests of the towhee or warbler experiencing high predation, while the cavity nests of chickadees experience very low risk of predation. These differences in predation risk affect how long the young stay in the nest; species like the towhee and warbler leave their risky nest 8 to 11 days after hatch, while chickadees do not leave their safe cavity nest until 20 to 22 days after hatch. As a result, the towhee and warbler young cannot fly when they leave their nest, while the chickadees are fully flight capable when they leave. These differences in developmental state of the young when they leave the nest also potentially affect how quickly they start feeding themselves, with the chickadees potentially feeding themselves within a few days after leaving the nest, while the towhee may take 3 weeks to develop this ability. Potentially, towhee parents must work much harder for each young to provide all their food compared with the chickadee where young almost immediately start obtaining some of their own food and can follow parents to reduce their travel. The extent to which parents are willing to work differs among species depending on their risk of mortality over their annual cycle. Taken together, these effects may explain why species differ in the number of young they attempt to raise, and has critical consequences for population dynamics of species. The proposed work will use observational and experimental approaches to testing these hypotheses.The fledgling period (after offspring leave the nest) is a critical period for demography, but interspecific variation in survival is unknown and documentation will aid understanding of population vulnerabilities to changing environmental conditions. Given the documented economic and aesthetic importance of birding to society, this conservation knowledge is important. Three graduate students whose thesis research will be supported by this project will be trained. Each year, 1 technician and 6 undergraduates will be trained in field techniques and the conduct of science, as well as 8 undergraduates from across disciplines (in and outside of biology) to transcribe videos of parental behaviors. The latter provides outreach to engage diverse students in scientific principles. Students will be educated through discussion sessions that will be used to teach the scientific principles for the work being conducted. To identify possible recruits, we will use broad advertising approaches to further enhance the diversity of social and cultural groups from which we can recruit. Finally, nests provide a rich source of video opportunities to demonstrate differences among species in social interactions, as well as intriguing videos of predation events. The researcher started obtaining short, high definition videos to develop an educational series on parental and offspring behaviors and predation events to put on YouTube for public outreach. PBS Nature is filming a documentary on nest architecture and avian family life that will include footage at the focal field site to further increase public outreach.