Farnsworth Jason M, Baasch David M, Farrell Patrick D
Platte River Recovery Implementation Program, 4111 4 Avenue, Suite 6, Kearney, Nebraska 68845, United States.
Heliyon. 2018 Jun 5;4(6):e00648. doi: 10.1016/j.heliyon.2018.e00648. eCollection 2018 Jun.
The Federally endangered interior least tern () and threatened piping plover () nest on emergent sandbars in several braided rivers in the USA. Previous habitat selection and geomorphic investigations identified a relationship between channel width and nesting incidence. Species-centric analyses indicate selection for the widest available channels whereas geomorphic-centric analyses indicate the probability of species occurrence was higher in narrow channels that better supported suitable sandbar habitat. Given the disparate conclusions from each of these perspectives, we examined species use in relation to channel-width metrics across segments of the Platte, Niobrara, and Loup Rivers from both perspectives. We found the probability of nesting incidence increased with increased maximum unvegetated channel width in all river segments. However, maximum unvegetated width decreased with increased total channel width once total width exceeded 300 m in the central Platte River and 500 m in all other river segments as did the probability that the channel was free of permanently-vegetated islands. Channels within the Lower Platte, Loup and Niobrara River systems with total widths of 500-800 m appear to be both wide enough to have a high probability of nesting incidence and narrow enough to be free of vegetated islands. Actions that affect channels with total, bank-to-bank widths of <500 m and >800 m would likely have a small influence on species use while actions that change the width characteristics of 500-800 m channels could have a strong negative or positive influence on species use. Integrating species- and geomorphic-centric views into a single analysis provided a fuller picture of the relationship between species use and channel-width metrics.
联邦濒危物种内陆 least tern（）和受威胁物种笛鸻（）在美国几条辫状河的露出沙洲上筑巢。先前的栖息地选择和地貌调查确定了河道宽度与筑巢发生率之间的关系。以物种为中心的分析表明，它们会选择最宽的可用河道，而以地貌为中心的分析表明，在能更好地支持适宜沙洲栖息地的较窄河道中，物种出现的概率更高。鉴于这两种观点得出的结论不同，我们从这两个角度研究了普拉特河、尼奥布拉拉河和卢普河各河段与河道宽度指标相关的物种利用情况。我们发现，在所有河段，筑巢发生率的概率都随着最大无植被河道宽度的增加而增加。然而，一旦总宽度在普拉特河中部超过300米，在所有其他河段超过500米，最大无植被宽度就会随着总河道宽度的增加而减小，河道没有永久性植被岛屿的概率也会减小。普拉特河下游、卢普河和尼奥布拉拉河水系中总宽度为500 - 800米的河道，似乎既宽到足以有较高的筑巢发生率概率，又窄到没有植被岛屿。影响岸到岸总宽度小于500米和大于800米的河道的行动，可能对物种利用影响较小，而改变500 - 800米河道宽度特征的行动，可能对物种利用产生强烈的负面或正面影响。将以物种为中心和以地貌为中心的观点整合到单一分析中，能更全面地呈现物种利用与河道宽度指标之间的关系。
