Delayed Dispersal: Teasing Apart the Effects of Resources and Parents

和人类一样，鸟类的幼崽有时在正常的独立年龄之后很长时间仍留在家里与父母在一起。在人类农业社会中，通常是男性，特别是长子，留在家里，家庭财富的程度（以农田衡量）是一个关键因素。在鸟类中，雄性也往往是呆在家里的性别，这导致了各种有趣的结果，包括合作繁殖，儿子在父母的巢里喂养小鸡，或者不太明显的社会行为，如公共栖息，合作保卫领土，家庭成员分享食物。像人类一样，西方蓝鸟？以防御领地的形式种植槲寄生，在冬天提供持续的浆果供应。像农民一样，蓝知更鸟也会种植植物。槲寄生的种子通过它们的内脏传递浆果，使种子仍然可以存活，并被一层粘稠的涂层包围，帮助它们附着在树枝上生长。西方蓝鸟的儿子和一些女儿在出生后的第一年倾向于和父母呆在家里。当槲寄生数量减少一半时，留在家里的后代就更少了，这表明在西方蓝鸟中，和人类一样，财富在延迟扩散中起着作用。目前的工作将确定父母的偏爱是否也为留在家里的儿子提供了优势，以及在留下的过程中，儿子是否会以与亲属竞争加剧的形式产生适应性成本，因乱伦而降低后代生存能力的遗传成本，以及因避免乱伦而降低配偶可获得性的遗传成本。对这些因素的研究将使西部蓝鸟延迟迁徙的图景更加完整，并有助于区分哪一个因素对儿子们留在家里更重要。资源或者与裙带关系的父母生活在一起而获得这些资源的机会增加。它还将确定槲寄生在多大程度上是对西部蓝鸟保护至关重要的关键资源。

In birds, as in humans, young sometimes remain at home with their parents long after the usual age of independence. In human agricultural societies, it is usually males, particularly first-born sons, that remain at home and the extent of family wealth, measured as farmland, is a key factor. Males also tend to be the gender that stays home in birds and this leads to a variety of interesting consequences, including cooperative breeding, where sons provide aid by feeding chicks in their parents' nest, or less obvious social behaviors such as communal roosting, cooperative defense of the territory, and food-sharing by family members. Like humans, western bluebirds ?own? land in the form of defended territories with mistletoe, which provides a continuous supply of berries over the winter. Like farmers, the bluebirds ?plant? the seeds of mistletoe by passing the berries through their guts, leaving the seeds still viable and surrounded by a sticky coating that helps them to adhere to limbs and grow. Western bluebird sons and some daughters tend to stay home with their parents during their first year of life. When mistletoe abundance was reduced by half, fewer sons stayed home, suggesting that in western bluebirds, as in humans, wealth plays a role in delayed dispersal. The current work will determine whether parental favoritism also provides advantages to sons staying at home and whether in staying, sons incur fitness costs in the form of increased competition with relatives, genetic costs of reduced offspring viability due to incest, and reduced mate availability due to incest avoidance. Studying these factors will complete the picture of delayed dispersal for western bluebirds and help tease apart which is more important to sons staying home ? resources or the increased access to those resources that comes from living with nepotistic parents. It will also establish the extent to which mistletoe is a keystone resource that is critical for western bluebird conservation.