DISSERTATION RESEARCH: Fitness Cost of Nest Defense: A Trade-Off With Offspring Care?

论文研究：雀鸟巢防御的适应性成本：与后代保育的权衡？PI: Stephen Nowicki & Renee A. duckworth在许多生物体中，幼体的生长和生存能力取决于它们从父母那里得到的照顾。尽管父母的照顾对后代的生存很重要，但成年人在提供照顾的数量和质量上往往差别很大。观察到这种差异的原因之一可能是因为个体在使用时间和资源来照顾亲代和其他活动方面面临权衡。最近在西部蓝鸟（Sialia mexicana）中记录了鸟巢防御行为表达的适应性成本。蓝鸟从保护它们的巢穴免受竞争中获益，因为合适的繁殖穴是有限的资源。然而，雄性西部蓝知更鸟更积极地保护它们的巢穴，平均每年产生的后代更少。提出的研究考察了三种可供选择的假设，这些假设可以解释观察到的巢保护行为与繁殖成功之间的关系。具体来说，它测试了在照顾后代和保护后代之间是否存在时间/精力的权衡，攻击性雄性是否天生就是较差的父母，或者海拔和巢穴防御之间的相关性是否最好地解释了巢穴防御和繁殖成功之间的关系。确定产生父母成功养育后代能力差异的机制对于我们理解亲代投资策略的演变至关重要。

DISSERTATION RESEARCH: FITNESS COST OF NEST DEFENSE IN A PASSERINE BIRD: A TRADE-OFF WITH OFFSPRING CARE?PI: Stephen Nowicki & Renee A. DuckworthIn many organisms, the ability of young to grow and survive depends on the care they receive from their parents. Despite the importance of parental care for offspring survival, adults often vary widely in the quantity and quality of care they provide. One of the reasons why this variation is observed may be because individuals face a trade-off in the use of their time and resources for parental care and for other activities. A fitness cost to the expression of nest defense behavior was recently documented in western bluebirds (Sialia mexicana). Bluebirds benefit from defending their nest cavities from competitors because suitable breeding cavities are a limited resource. However, male western bluebirds that defend their nests more aggressively produce fewer offspring on average each year. The proposed research examines three alternative hypotheses that could account for this observed relationship between nest defense behavior and reproductive success. Specifically, it tests whether there is a time/energy trade-off between offspring care and defense, whether aggressive males are inherently poorer parents, or whether a correlation between elevation and nest defense best explains the relationship between nest defense and reproductive success. Identifying the mechanisms that produce variation in parents' ability to raise young successfully is essential for our understanding of the evolution of parental investment strategies.