Utah Museum of Natural History, University of Utah, Salt Lake City, UT 84112, USA.
Proc Natl Acad Sci U S A. 2011 Jul 12;108(28):11488-93. doi: 10.1073/pnas.1104955108. Epub 2011 Jun 27.
Ecologists have long hypothesized that fragmentation of tropical landscapes reduces avian nest success. However, this hypothesis has not been rigorously assessed because of the difficulty of finding large numbers of well-hidden nests in tropical forests. Here we report that in the East Usambara Mountains in Tanzania, which are part of the Eastern Arc Mountains, a global biodiversity hotspot, that daily nest survival rate and nest success for seven of eight common understory bird species that we examined over a single breeding season were significantly lower in fragmented than in continuous forest, with the odds of nest failure for these seven species ranging from 1.9 to 196.8 times higher in fragmented than continuous forest. Cup-shaped nests were particularly vulnerable in fragments. We then examined over six breeding seasons and 14 study sites in a multivariable survival analysis the influence of landscape structure and nest location on daily nest survival for 13 common species representing 1,272 nests and four nest types (plate, cup, dome, and pouch). Across species and nest types, area, distance of nest to edge, and nest height had a dominant influence on daily nest survival, with area being positively related to nest survival and distance of nest to edge and nest height being both positively and negatively associated with daily nest survival. Our results indicate that multiple environmental factors contribute to reduce nest survival within a tropical understory bird community in a fragmented landscape and that maintaining large continuous forest is important for enhancing nest survival for Afrotropical understory birds.
生态学家长期以来一直假设，热带景观的破碎化会降低鸟类筑巢的成功率。然而，由于在热带森林中很难找到大量隐藏良好的巢穴，因此这一假设尚未得到严格评估。在这里，我们报告说，在坦桑尼亚的东乌桑巴拉山脉（属于东非弧形山脉这一全球生物多样性热点地区），我们在一个繁殖季节内对 8 种常见的下层鸟类中的 7 种进行了研究，发现这些鸟类的每日巢存活率和巢成功率在破碎化森林中显著低于连续森林，这 7 种鸟类的巢失败概率比连续森林高 1.9 到 196.8 倍。杯状巢在碎片中特别脆弱。然后，我们在六个繁殖季节和 14 个研究地点进行了多变量生存分析，研究了景观结构和巢位置对 13 种常见鸟类的每日巢存活率的影响，这些鸟类代表了 1272 个巢和四种巢型（盘状、杯状、圆顶状和袋状）。在物种和巢型方面，面积、巢与边缘的距离和巢的高度对每日巢存活率有主要影响，面积与巢存活率呈正相关，而巢与边缘的距离和巢的高度与每日巢存活率呈正相关和负相关。我们的结果表明，在破碎化的热带下层鸟类群落中，多个环境因素会降低巢的存活率，而保持大面积的连续森林对于提高非洲热带下层鸟类的巢存活率非常重要。
