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首页> 外文期刊>Journal of Wildlife Management >Nest success and cause-specific nest failure of grassland passerines breeding in prairie grazed by livestock.
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Nest success and cause-specific nest failure of grassland passerines breeding in prairie grazed by livestock.

机译：放牧草地上草原雀形目繁殖的成巢成功和特定原因的成巢失败。

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摘要

Livestock grazing is a widespread source of habitat modification, and may affect populations of ground-nesting grassland birds by influencing rates of nest failure. Nesting attempts can fail for various reasons, and determining risk of failure from specific causes associated with livestock grazing would enhance development of range management practices in areas managed for threatened grassland bird populations. Domestic livestock may influence nest failure by affecting vegetation structure, numerical or functional responses of predators, or directly by trampling nests. We hypothesized stocking rate may influence nest fate because it affects the amount and distribution of remaining vegetation, and the number of large herbivores to which nests are exposed. In 2007 and 2008, we evaluated nest fates for savannah sparrows and horned larks under 4 stocking rates experimentally applied in 40-ha paddocks in northeastern Oregon, USA. In addition to stocking rate, we evaluated variables such as vegetation structure and predator abundance and activity to help clarify mechanisms responsible for nest failure. We used a discrete competing risks framework to estimate daily probability of nest survival and failure from specific causes. These algorithms, implemented in a stand-alone graphical user interface-driven model, allow incorporation of covariates within an information theoretic approach to model inference. Although stocking rate influenced vegetation structure, the only nest failures related to stocking rate were from trampling. Trampling events were too infrequent to test for treatment effects (only 1 nest of each species), but occurred in the moderate and high stocking treatments. Additional variables were related to variation in nest failure from predation, but we found no support for the hypothesis that these causes of failure were affected by stocking rate. For savannah sparrows, daily probability of nest success (95% CI)=0.97 (0.96-0.98); predation=0.018 (0.008-0.028); and trampling=0.001 (0.000-0.004). For horned larks, daily probability of nest success=0.96 (0.95-0.98); predation=0.029 (0.012-0.045); and trampling=0.003 (0.000-0.007). Our results suggest grasslands managed for livestock may generally be compatible with grassland songbird conservation, at least for the species and stocking rates examined here. The most effective conservation strategies for improving nest success will involve decreasing risk of nest predation. However, we found no evidence that management of stocking rate is an effective method for doing so.Digital Object Identifier http://dx.doi.org/10.1002/jwmg.437
机译：放牧牲畜是改变栖息地的广泛来源，并可能通过影响筑巢失败率来影响地面嵌套的草地鸟类的数量。筑巢尝试可能由于各种原因而失败，而确定与牲畜放牧相关的特定原因而导致失败的风险将增强针对濒临灭绝的草地鸟类种群管理的区域范围管理做法的发展。家畜可能通过影响植被结构，捕食者的数量或功能响应或直接践踏巢穴来影响巢穴破坏。我们假设放养率可能会影响巢穴的命运，因为它会影响剩余植被的数量和分布以及巢穴所暴露的大型草食动物的数量。在2007年和2008年，我们评估了在美国俄勒冈州东北部40公顷围场中实验应用的4种放养率下大草原麻雀和有角的百灵的巢命运。除了放养率之外，我们还评估了诸如植被结构，捕食者丰度和活动度之类的变量，以帮助阐明造成巢灾的机制。我们使用了离散竞争风险框架来估计因特定原因造成的巢生存和失败的日概率。在独立的图形用户界面驱动的模型中实现的这些算法允许将协变量并入信息理论方法中以进行模型推断。尽管放养率影响植被结构，但与放养率有关的唯一巢害是践踏。踩踏事件很少发生，无法测试处理效果（每个物种只有1个巢），但发生在中度和高放养处理中。其他变量与捕食导致的巢破坏的变化有关，但是我们发现这些失败原因受放养率影响的假设没有得到支持。对于大草原麻雀，每日成功成巢的可能性（95％CI）= 0.97（0.96-0.98）;掠食= 0.018（0.008-0.028）;和践踏= 0.001（0.000-0.004）。对于有角的百灵鸟，巢成功的日概率为0.96（0.95-0.98）;捕食= 0.029（0.012-0.045）;和践踏= 0.003（0.000-0.007）。我们的结果表明，为牲畜管理的草原通常与草原鸣鸟的保护兼容，至少对于这里所研究的物种和放养率而言。提高巢穴成功率的最有效的保护策略将涉及降低巢穴捕食的风险。但是，我们没有找到证据证明库存率管理是一种有效的方法。Digital Object Identifier http://dx.doi.org/10.1002/jwmg.437

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