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

9904058生境破碎化从根本上影响着群落结构和营养相互作用。大量关于森林鸟类的研究支持了一个广为接受的观点，即繁殖栖息地的碎片化大大降低了每年的繁殖成功率。这种效应背后的机制通常被报道为巢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、斑块特异性的碎片化特征上，如到边缘的距离和斑块大小。很少考虑到森林碎片以外的更广阔的景观。事实上，最近的证据表明，破碎化对森林鸟类的影响随景观构成而变化。人们对当地过程和景观过程之间的相互作用了解甚少，但由于许多过程与森林破碎化的程度共同变化，因此它们之间的相互作用可能很复杂。本研究将直接评估景观组成如何影响伊利诺斯州南部鸟类筑巢破碎化的结果。该地区拥有超过50万公顷的森林，其景观在森林覆盖率和不同非森林覆盖类型（作物与草地）的相对覆盖率方面差异很大。本研究首先对森林斑块周围的生境类型进行分类。然后，将在四种不同的景观（草地或作物基质的高碎片化和低碎片化）中选择重复斑块，测量鸣禽繁殖成功的研究。影响鸣禽繁殖成功的因素包括：雏鸟寄生、巢穴捕食和鹿群对林下植被的改变。然后，这些因素将被量化，并与繁殖成功有关。这项研究的结果将为地方和区域保护战略提供信息，并将构成一个独特的历史案例，说明地方人口进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.