Are Effects of Forest Fragmentation on Avian Nesting Success Mediated by Landscape Composition

罗宾逊生境破碎化从根本上影响群落结构和营养相互作用。许多对森林鸟类的研究支持了普遍持有的观点，即繁殖栖息地的碎片化显著降低了年度繁殖成功。这种效应背后的机制通常被报道为巢穴捕食率和幼虫寄生率的增加。尽管如此，大多数研究都集中在局部的、特定于斑块的碎片特征上，如到边缘的距离和区域大小。对森林碎片以外更广泛的景观考虑较少。事实上，最近的证据表明，碎片化对森林鸟类的影响随着景观组成的变化而变化。当地和景观过程之间的相互作用知之甚少，但可能很复杂，因为许多过程随着森林碎片化的程度而不同。这项研究将直接评估景观构成如何影响伊利诺伊州南部鸟类筑巢的碎片化结果。该区域拥有50多万公顷森林，其森林复盖量和不同非森林复盖物类型(作物与草地)的相对复盖率差别很大。本研究将首先对森林斑块周围的生境类型进行分类。然后，将在四个不同的景观(草原或作物基质中的高和低碎片化)中选择重复斑块，在其中将测量鸣鸟繁殖成功的研究。影响鸣禽繁殖成功的因素包括幼鸟寄生、巢内捕食和鹿觅食对林下植被的改变。然后，这些因素将被量化，并与生殖成功相关。这项研究的结果将为当地和区域的保护战略提供参考，并将构成一个独特的案例历史，说明当地人口过程如何以及为什么可以以更大规模的现象为条件。

9904058RobinsonHabitat fragmentation fundamentally affects community structure and trophic interactions. Numerous studies of forest birds support the widely held notion that the fragmentation of breeding habitat significantly decreases annual reproductive success. The mechanisms underlying this effect are generally reported as increased rates of nest predation and brood parasitism. Nonetheless, most studies have focuses on local, patch-specific features of fragmentation such as distance to edge and tract size. Less consideration has been given to the broader landscape outside forest fragments. Indeed, recent evidence suggests that the effects of fragmentation on forest birds change with landscape composition. Interactions between local and landscape processes are poorly understood, but potentially complex because many processes co-vary with the magnitude of forest fragmentation. This study will assess directly how landscape composition affects the outcome of fragmentation on birds nesting in southern Illinois. This region contains over 500,000 ha of forest in landscapes that vary widely in the amount of forest cover and relative coverage of different non-forest cover types (crops versus grassland). This study will first classify habitat type surrounding forest patches. Then, replicate patches will be selected in four different landscapes (high and low fragmentation in grassland or crop matrix) in which studies of reproductive success of songbirds will be measured. Factors affecting song bird reproductive success include brood parasitism, nest predation and alteration of understory vegetation by deer browsing. These factors will then be quantified and related to reproductive success. Results of this study will inform local and regional conservation strategies and will constitute a unique case history of how and why local demographic processes can be conditional upon larger-scale phenomena.