Landscape-level Population Dynamics of an Avian Habitat Specialist Invading an Alien Grassland in Southeastern Arizona

由于干旱和过度放牧，波特里麻雀几乎从美国西南部消失了。这种鸟是一种高草专家，现在通常被限制在低地地区散布的草地上。在这片可以长出2米多高的原生草原上，这些鸟把巢藏在这些高大的草根上，躲避捕食者，然后在邻近的山坡上觅食蝗虫和其他昆虫。最近，这些鸟开始在当地的高原草原地区筑巢，那里的草比散布在草地上的高大的草要矮，但蝗虫密度很高。此外，它们还在盖子以引进的非洲牧草为主的地区筑巢，那里的盖子几乎和本土散布草一样重。然而，在这些地区，蚱蜢相对稀少。这种独特的情况允许对景观生态、汇/源和集合种群动态以及外来植被的生态影响的假设和预测进行检验。这项研究将回答这样的问题：草盖(安全的筑巢栖息地)和食物可获得性(高蝗虫数量)对波特里麻雀繁殖成功的相对重要性是什么？三种栖息地(萨卡顿、本地高地草原和外来草原)对波特里麻雀区域种群动态的共同贡献是什么，以及它们与其活动范围北缘整个物种种群的汇/源状况有何关系？此外，它还将讨论外来草原是否代表了鸟类的合适栖息地，或者引入的草原是否是该物种的生态陷阱。

9815293BockThe Botteri's sparrow has almost disappeared from the American Southwest due to drought and overgrazing. This bird, a tallgrass specialist, is usually now restricted to stands of scaton grass in lowland areas. In this native grassland that can grow over 2 meters tall, the birds conceal their nests from predators at the bases of these tall grasses and then forage on adjacent slopes for grasshoppers and other insects. Recently, these birds have begun nesting in native upland grassland areas where the grasses are shorter than the tall stands of scaton grass, but grasshopper densities are high. In addition, they also nest in areas where the cover is dominated by introduced African lovegrass, where the cover is nearly as heavy as the native scaton. However, in these areas, grasshoppers are relatively scarce. This unique situation allows for testing of hypotheses and predictions of landscape ecology, sink/source and metapopulation dynamics and the ecological impacts of alien vegetation. This research will answer such questions as: What is the relative importance of grass cover (safe nesting habitat) versus food availability (high grasshopper numbers) to reproductive success in the Botteri sparrow? What are the combined contributions of the three habitats (sacaton, native upland grasslands and exotic grassland) to regional population dynamics of the Botteri sparrow and how these relate to the sink/source status of the entire species population at the northern margin of its range? In addition, it will address whether the exotic grasslands represent a suitable habitat for the birds or are the introduced grasslands an ecological trap for this species.