DISSERTATION RESEARCH: Interspecific Competition Increases Cooperative Group Sizes in Brown-headed Nuthatches (Sitta pusilla).

棕色头的nuthatches生活和家庭群体繁殖。这些家庭群体似乎共同努力，以保护筑巢洞，从其他物种也需要在树上筑巢洞。由于nuthatches是小型鸟类（10克），如果他们不合作，他们经常失去他们的巢较大的物种。这个项目试图了解如果合作防御巢洞的棕头nuthatches增加了后代的数量，他们贡献给下一代。合作繁殖者经常与亲属合作，因为外部繁殖机会很少，目前还不清楚这种合作是否是一种适应性策略，或者鸟类是否只是在恶劣的情况下尽力而为。这个项目通过测试合作的nuthatches是否真的比非合作者有更多的后代来解决这些替代品。因此，该项目可以揭示合作育种的潜在新效益，它还提供了关于褐头裸帽草自然历史的信息，这是一种面临全球变暖和城市化双重威胁的物种。这个项目已经增加了当地的棕色头nuthatches人口规模，联合首席研究员将继续参与该物种的保护工作，在农贸市场的摊位上非正式地发言，并鼓励当地人在他们的财产上放置nuthatchs大小的盒子。 本项目测试了以前未经测试的想法，种间竞争功能作为一个重要的选择力量对群体大小的棕头（BHNU，Sitta pusilla）。关键的假设是，同等大小的竞争对手之间的竞争影响合作育种的利益，并选择更大的群体规模。通过揭示与其他物种的竞争如何影响不同竞争压力下群体成员的包容性适合度，以及在各种群体规模下，该项目测试了异种竞争是否可以增加BHNUs在群体中的适合度，从而选择增加合作群体规模。合作育种存在的一个传统假设是，生态约束阻止独立育种和驱动器的群体规模的增加，预测的包容性适合度的个人将减少群体规模的增加。然而，这个项目的动机假设，即健身增加群体规模的增加，通过在异种防御辅助功效，预测完全相反的模式。遗传亲子关系的确定，和计算的包容性健身，将使这项研究区分生态约束和异源防御效益的驱动程序，增加组大小的合作育种BHNU。

Brown-headed nuthatches live and breed in family groups. These family groups appear to work together to defend nesting holes from other species that also need holes in trees to nest. Since nuthatches are small birds (10 g), they often lose their nests to larger species if they do not cooperate. This project seeks to understand if cooperative defense of nesting holes by brown-headed nuthatches increases the number of offspring they contribute to the next generation. Cooperative breeders often cooperate with relatives because outside opportunities for breeding are rare, and it is unclear whether this cooperation is an adaptive strategy or whether the birds are simply making the best of a bad situation. This project addresses those alternatives by testing whether cooperating nuthatches actually have more offspring than non-cooperators. This project therefore could uncover a potential new benefit of cooperative breeding, and it also provides information on the natural history of brown-headed nuthatches, a species facing the dual threats of global warming and urbanization. This project has already increased local population sizes of brown-headed nuthatches, and the Co-Principal Investigator will continue to participate in conservation efforts for this species by speaking informally at a farmer's market booth and encouraging locals to place nuthatch-sized boxes out on their property. This project tests the previously untested idea that interspecific competition functions as an important selective force on group size in the Brown-headed nuthatch (BHNU, Sitta pusilla). The key hypothesis is that competition among equally sized competitors influences the benefits of cooperative breeding and selects for larger group sizes. By uncovering how competition with other species impacts inclusive fitness for group members under differing competitive pressures, and at various group sizes, this project tests whether heterospecific competition can increase the fitness of BHNUs in groups, and thus select for increased cooperative group sizes. A traditional hypothesis for the existence of cooperative breeding is that ecological constraints prevent independent breeding and drive increases in group size, predicting that the inclusive fitness of individuals will decrease as group sizes increase. However, the motivating hypothesis of this project, that fitness increases as group size increases through helper efficacy in heterospecific defense, predicts exactly the opposite pattern. Genetic parentage determination, and the calculation of inclusive fitness, will allow this research to distinguish between ecological constraints and heterospecific defense benefits as drivers of increased group size in the cooperatively breeding BHNU.