Mating and Parasitic Behavior of Brown-Headed Cowbirds

摘要 PI：阿什利提案编号：9601201 褐头牛鹂的交配和寄生行为 将通过全面的实地和实验室研究调查褐头燕八哥的繁殖生物学。 无论是交配系统和寄生的做法，个别女性燕八哥将分配亲子关系，以450-500燕八哥蛋和雏鸟收集在一个现场在莫顿植物园在莱尔伊利诺伊州从映射的巢位置进行研究。 这将通过DNA微卫星基因分型完成，其允许通过排除来确定亲子关系。 遗传数据将用于确定燕八哥在本研究中心是否一夫一妻制，如以前报道的那样，或混杂。 像褐头燕八哥这样的寄生虫没有父母的照顾，这使得一夫一妻制在理论上是不可能的。 如果确定燕八哥确实是一夫一妻制，那么可能需要重新评估鸟类交配系统的流行理论。 遗传分析也将被用来测试的假设，即女性燕八哥限制产卵的可定义的领域，在很大程度上是不重叠。不重叠的生殖区域表明竞争有限的资源，宿主巢。 这将通过绘制分配给单个雌性的后代的位置并将其与其他雌性后代的分布进行比较来完成。 本研究地点以前的实地工作表明，燕八哥差异寄生在某些宿主物种的巢时，多个主机。 几个生态因素，包括栖息地，巢型，主机的大小和主机防御与观察到的寄生率密切相关。 拟议的研究将检查这些模式在多大程度上反映了雌性燕八哥的行为适应（例如宿主选择）。 将进行两项相关的田间研究，以确定雌虫是否优先寄生最高质量的宿主物种和/或避免低质量的宿主物种，例如已知会从巢中排出燕八哥卵的物种（Rrejectors）。 第一个实地研究将确定不同的常见寄生宿主物种的相对能力，成功地培育燕八哥雏鸟。不同的主机作为燕八哥代理人的相对质量将进行比较，观察到的寄生模式，以确定是否高品质的主机物种被选择性寄生。 第二项实地研究将确定RrejectorS物种的寄生率。 在我们的研究地点，我们已经观察到三种已知会排出燕八哥卵的宿主的寄生现象，这表明雌性燕八哥并没有完全避开这些宿主物种。 通过实验寄生这些物种的巢穴，将确定产卵的速度。 从这一措施和观察到的寄生率，我们可以确定燕八哥是否喜欢受体宿主物种拒绝，或者，未能区分这些低质量的主机。 展示宿主选择模式对于理解宿主-寄生虫协同进化和制定保护策略以保护受燕八哥威胁的宿主物种都很重要。

ABSTRACT PI: ASHLEY PROPOSAL NUMBER: 9601201 Mating and Parasitic Behavior of Brown-headed Cowbirds The breeding biology of the brown-headed cowbird, Molothrus ater, will be investigated through a comprehensive field and laboratory study. Both the mating system and the parasitism practices of individual female cowbirds will be studied by assigning parentage to 450-500 cowbird eggs and nestlings collected at a field site at the Morton Arboretum in Lisle Illinois from mapped nest locations. This will be done by DNA microsatellite genotyping, which allows parentage to be determined by exclusion. The genetic data will be used to determine whether cowbirds at this study site mate monogamously, as has been previously reported, or promiscuously. Brood parasites such as the brown-headed cowbird are freed from parental care, which makes monogamy theoretically improbable. If it is determined that cowbirds are indeed monogamous, prevailing theories of avian mating systems may need to be reevaluated. The genetic analysis will also be used to test the hypothesis that female cowbirds restrict egg-laying to definable areas that are largely non-overlapping. Non-overlapping reproductive areas would suggest competition for a limited resource, host nests. This will be done by mapping the locations of offspring assigned to an individual female and comparing these to distributions of other femalesU offspring. Previous field work at this study site demonstrates that cowbirds differentially parasitize the nests of certain host species when multiple hosts are available. Several ecological factors including habitat, nest type, host size, and host defenses are strongly correlated with observed rates of parasitism. The proposed study will examine the extent to which these patterns reflect behavioral adaptations (e.g. host choice) of female cowbirds. Two related field studies will be conducted to determine if fem ales preferentially parasitize the highest quality host species and/or avoid low quality host species such as those known to eject cowbird eggs from their nests (RrejectorsS). The first field study will determine the relative abilities of different commonly parasitized host species to successfully foster cowbird nestlings. The relative qualities of different hosts as cowbird surrogates will be compared to observed patterns of parasitism to determine if high-quality host species are selectively parasitized. The second field study will determine parasitism rates of RrejectorS species. At our study site we have observed parasitism of three species of hosts known to eject cowbird eggs, indicating that female cowbirds are not completely avoiding these host species. By experimentally parasitizing the nests of these species, the rate of egg-ejection will be determined. From this measure and the observed rate of parasitism, we can ascertain whether cowbirds prefer acceptor host species over rejectors, or alternatively, fail to discriminate against these low-quality hosts. Demonstrating patterns of host choice is important both for understanding host-parasite coevolution and for developing conservation strategies to protect host species threatened by cowbirds.