DISSERTATION RESEARCH: Effects of Habitat Heterogeneity on Songbird Fecundity in an Experimental Landscape

景观异质性促进了自然生态系统中更高的生物多样性。在北美，由于火和大型食草动物(包括野牛、麋鹿和叉角羚)选择性放牧之间的相互作用，Tallgras草原历来是不同栖息地的马赛克。近几十年来，农业集约化导致管理草原上的景观更加均匀，这与北美和欧洲鸣鸟数量的普遍下降有关。草原异质性的丧失可能会改变食物的可获得性、捕食风险或褐头牛鸟(Molothrus Ater)的幼鸟寄生率，从而对鸟类产生重大影响。拟议的野外研究将评估栖息地异质性对受到保护关注的鸣禽Dickcissel(Spiza Americana)幼鸟活动和生存的影响。该项目将有助于更好地了解受管理草原上草原鸣禽的繁殖生态，并有助于了解草原管理与生态、鸟类种群和保护之间的关系。这项实地研究将在堪萨斯州东部和俄克拉何马州的弗林特山生态区进行，那里仍有大片原生高草草原，但栖息地质量受到牧场管理持续变化的影响。Konza Prairie是美国国家科学基金会资助的位于弗林特丘陵北部的长期生态研究(LTER)站点，提供了一个独特的实验景观，通过长期放牧和火灾处理创造了不同程度的栖息地异质性。斑块焚烧放牧管理增加了营养结构的异质性，因为在三年轮换计划中，每年只有三分之一的牧场被焚烧，而且放牧牛的活动不受限制。第四个牧场每年被烧毁，放牧时间长达一季，这将是一个负面对照，而第五个牧场，每年被烧毁但不放牧，将是一个积极的对照。研究人员将在五种实验治疗方法中，为总共60只雏鸟安装小型无线电发射器。在离开鸟巢后的头30天里，幼鸟将每天被重新安置，以确定活动和存活情况。这项研究将使用野外方法和统计分析来估计幼鸟的活动、节肢动物猎物的可用性和幼鸟的存活率。了解生物因素如何与鸟巢和雏鸟存活等人口统计参数相互作用，将有助于理解景观异质性对鸟类生活史策略的作用。

Landscape heterogeneity promotes higher biodiversity in natural ecosystems. In North America, tallgrass prairie was historically maintained as a mosaic of different habitats by the interaction between fire and selective grazing by large herbivores, including bison, elk and pronghorn. In recent decades, agricultural intensification has led to more homogeneous landscapes in managed grasslands, which has been linked to widespread declines in songbird populations in North America and Europe. A loss of heterogeneity in grasslands could have major consequences for birds by changing food availability, predation risk, or rates of brood parasitism by Brown-headed Cowbirds (Molothrus ater). The proposed field study will estimate the effects of habitat heterogeneity on movements and survival of juvenile Dickcissels (Spiza americana), a songbird of conservation concern. The project will provide a better understanding of the reproductive ecology of grassland songbirds in managed grasslands, and will aid in understanding the relationships among grassland management and ecology, bird populations, and conservation. This field study will be conducted in the Flint Hills ecoregion of eastern Kansas and Oklahoma, where large tracts of native tallgrass prairie still remain, however habitat quality has been impacted by ongoing changes in rangeland management. Konza Prairie is an NSF-funded Long-term Ecological Research (LTER) site in the northern Flint Hills, and provides a unique experimental landscape with different levels of habitat heterogeneity created by long-term grazing and fire treatments. Patch-burn grazing management increases heterogeneity in vegetative structure because only a third of the pasture is burned each year in a three-year rotational scheme, and movements of grazing cattle are unrestricted. A fourth pasture with annual burns and season-long stocking of cattle will be a negative control, and a fifth pasture with annual burns but no grazing will be a positive control. The researchers will attach small radio-transmitters to a total of 60 fledglings, across the five experimental treatments. Fledglings will be re-located daily during the first 30 days after leaving the nest to determine movements and survival. The research will estimate fledgling movements, arthropod prey availability, and fledgling survival using field methods and statistical analyses. Understanding how biotic factors interact with demographic parameters like nest and fledgling survival will help to understand the role of landscape heterogeneity on the life-history strategies of birds.