The piping plover (Charadrius melodus) was listed under the United States Endangered Species Act (ESA) because of habitat loss and excessive predation. The Missouri River provides important habitat for the Great Plains population of the species, some of which nest and forage on river sandbars deposited naturally during high river flows. The United States Army Corps of Engineers (USACE) operates a series of dams on the river that affect water level and the size, number, distribution, and vegetative cover of these sandbars. As a federal agency, USACE is required by the ESA to have a program to conserve the piping plover, and is prohibited from engaging in activities that jeopardize the plover's continued existence. Pursuant to these obligations, the USACE implemented a habitat creation program on the Gavins Point Reach (GVP) and Lewis and Clark Lake (LCL) on the Missouri River from 2004 to 2011. This habitat creation provided an opportunity to study the piping plover's demographic response to several habitat types, and in particular to habitat creation. The goal of this study was to assess the effects of management on plovers using the Missouri River. We studied the changes in engineered and natural habitats, and compared the effects of newly engineered habitat versus naturally created habitat on plover demography during 2005–2011. To this end, we estimated changes in nesting habitat (open or sparsely vegetated dry sand) and examined the factors affecting nest success, chick survival from hatching to fledging, survival, and movement (between and among engineered and natural sandbars) of hatch‐year and adult birds, fidelity of plovers to the study area, and immigration of plovers into engineered habitat. We used demographic estimates to determine overall and habitat‐specific reproductive output and overall population growth rate. Under the assumption that plovers are habitat limited on the Missouri River, we predicted that they would respond positively to the creation of engineered habitat, that their demographic rates would be higher at those sites than on older, natural sandbars, and that over time, the rates would resemble those on older, natural habitats. Engineered sandbars had proportionally more plover nesting habitat than natural sandbars, but the proportion of nesting habitat decreased through vegetation encroachment and erosion as the sandbars aged. Adult and hatch‐year plovers immigrated to engineered sandbars, but immigration slowed as nesting density increased. Nesting density on engineered sandbars increased soon after sandbar construction, peaked 2–3 years later, and then declined to levels similar to those on older, natural sandbars. Birds that nested on engineered sandbars had higher nest success, and those nesting on LCL had higher chick survival than those that nested on GVP sandbars. Adult survival did not differ between engineered or natural habitat, but apparent survival was lower for birds that were not known to nest, indicating higher emigration or mortality rates for non‐nesters. Adult and hatch‐year plovers had high fidelity to the study area (>60% for hatch‐year birds, >90% for adults), and hatch‐year fidelity was highest (>80%) when habitat availability increased. We estimated that given observed survival rates, the reproductive output needed for a stationary population was 1.25 chicks fledged per pair, a rate which was equaled or exceeded in 3 of 4 years on LCL, in 2 of 5 years on engineered sandbars on GVP, and in 1 of 5 years on natural sandbars on GVP. Our results support the hypothesis that piping plovers were habitat‐limited before and during the study. Although nest exclosure and predator control sometimes can improve reproductive output, we predict that these interventions will do little to increase population size unless there is additional habitat to capture enhanced productivity. Based on high fidelity rates and short distances between subsequent nesting attempts (median = 12 km for adults), we suggest that habitat construction be widely distributed within approximately 12 km of a source population to maximize the efficiency of the population‐building process. © 2015 The Wildlife Society.

中文翻译：

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密西西比河对密苏里河上栖息地创造的人口响应

管道pl（Charadrius melodus）因栖息地丧失和过度捕食而被列入《美国濒危物种法》（ESA）。密苏里河为大平原物种的栖息地提供了重要的栖息地，其中一些在高流量期间自然沉积的河流沙洲上筑巢和觅食。美国陆军工程兵团（USACE）在河上经营着一系列水坝，这些水坝影响水位以及这些沙洲的大小，数量，分布和植被。作为联邦机构，欧洲航天局要求USACE制定一项计划，以保护管道pl鼠，并且不得从事危害the鼠继续生存的活动。根据这些义务，USACE于2004年至2011年在密苏里河的加文斯角河段（GVP）以及路易斯湖和克拉克湖（LCL）上实施了栖息地创建计划。该栖息地创建为研究管道pl对多种栖息地类型的人口统计学响应提供了机会，特别是栖息地的创造。这项研究的目的是评估使用密苏里河的管理对pl的影响。我们研究了工程栖息地和自然栖息地的变化，并比较了2005-2011年间新工程栖息地与自然栖息地对pl人口的影响。为此，我们估算了筑巢栖息地（开放或稀疏的干燥沙子）的变化，并研究了影响筑巢成功，从孵化到成雏的雏鸡存活率，孵化年和成年鸟类的活动和运动（在工程和天然沙洲之间和之中），pl对研究区域的保真度以及pl向工程化栖息地的迁移。我们使用人口统计学估算来确定总体和特定于栖息地的生殖产出以及总体人口增长率。在密苏里河栖息地受到限制的前提下，我们预测它们会对人工栖息地的建立产生积极的响应，这些地点的人口统计数据将比旧的天然沙洲高，随着时间的推移，费率类似于较旧的自然栖息地的费率。工程沙洲比自然沙洲具有更多的pl巢栖息地，但是随着沙洲老化，筑巢栖息地的比例由于植被侵占和侵蚀而减少。成年和孵化年的小鱼移居到工程沙洲，但随着巢密度的增加，移行速度减慢。工程沙洲的筑巢密度在沙洲建造后不久就增加了，在2-3年后达到顶峰，然后下降到与较旧的天然沙洲相似的水平。筑巢在工程沙洲上的鸟具有更高的筑巢成功率，而筑巢在LCL上的鸟比在GVP沙洲上筑巢的鸟具有更高的雏鸡存活率。在工程栖息地或自然栖息地之间，成年存活率没有差异，但是对于未知筑巢的鸟类，其表观存活率较低，这表明非巢鸟的迁徙或死亡率较高。成年和孵化期仔鱼对研究区域具有较高的保真度（孵化年禽> 60％，成年> 90％），并且当栖息地可用性增加时，孵化年保真度最高（> 80％）。我们估计，在观察到的存活率的情况下，固定种群所需的繁殖产量为每对1.25羽雏鸡，在LCL中4年中有3年等于或超过该比率，在GVP工程沙洲中5年中有2年等于或超过该比率。在GVP上的天然沙洲上行驶的5年中有1年 我们的结果支持以下假设：在研究之前和研究期间，管道over的栖息地受到限制。尽管鸟巢的排泄物和捕食者的控制有时可以改善繁殖产量，但我们预测，除非有其他栖息地来提高生产力，否则这些干预措施对增加种群规模几乎没有作用。基于高保真度和后续嵌套尝试之间的距离很短（成人的中位数= 12 km），我们建议将栖息地建设广泛分布在源种群的约12公里内，以最大程度地提高种群建设过程的效率。©2015野生动物协会。