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，高草草原在历史上是由火灾和大型食草动物（包括野牛、麋鹿和叉角羚）选择性放牧之间的相互作用维持的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的景观更加同质化，这与北美和欧洲鸣禽种群的普遍下降有关。草原异质性的丧失可能会对鸟类产生重大影响，改变食物供应，捕食风险，或由褐头牛鹂（Molothrus ater）的育雏寄生率。拟议的实地研究将估计栖息地异质性的影响，对运动和生存的少年Dickcissels（Spiza americana），鸣禽的保护问题。该项目将使人们更好地了解管理草原中草原鸣禽的生殖生态，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。这项实地研究将在东部堪萨斯和俄克拉荷马州的弗林特山生态区进行，那里仍然保留着大片的原生高草草原，但栖息地质量受到牧场管理持续变化的影响。Konza Prairie是位于弗林特山北方的一个由NSF资助的长期生态研究（LTER）基地，提供了一个独特的实验景观，长期放牧和火灾处理造成了不同程度的栖息地异质性。 斑烧放牧管理增加了植被结构的异质性，因为在三年轮换计划中，每年只有三分之一的牧场被烧毁，放牧牛的运动不受限制。第四个牧场每年烧伤和牛的季节性放养将是一个阴性对照，第五个牧场每年烧伤，但没有放牧将是一个阳性对照。研究人员将在五种实验性治疗方法中，为总共60只雏鸟安装小型无线电发射器。雏鸟离开巢穴后的头30天内，每天都会被重新安置，以确定它们的活动和生存情况。这项研究将估计羽翼未丰的运动，节肢动物猎物的可用性，和羽翼未丰的生存使用现场的方法和统计分析。了解生物因素如何与巢和雏鸟生存等人口参数相互作用，将有助于了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.