Toward assessing the effects of bank stabilization activities on wildlife communities of the upper Yellowstone River, U.S.A

Abstract

The upper Yellowstone River has been subject to multiple bank stabilization projects between Gardiner and Springdale, Montana, over the last 20 years. Additional channel modification activities are likely on the Yellowstone, and there is concern over the short- and long-term cumulative effects of channel modification activities on physical processes and dynamics of the river, associated riparian vegetation, and fish and wildlife resources that depend on the river. This document represents a first step toward conservation of the riparian vertebrate community on the upper Yellowstone River, with expected changes due to bank stabilization activities. Conservation strategies should be based on the life histocy attributes of the species of interest and the expected landscape changes for a specific geographic region. In this document, species accounts summarize the distribution, abundance, life histories, and habitat associations of 69 bird species, 4 amphibian species, 5 reptile species, and 9 species of mammals known or assumed to occur in the study area, including 38 species designated as species of interest. A matrix is presented to assist managers in evaluating the degree to which a species may be negatively affected by riverbank stabilization activities. The degree of vulnerability of birds to bank stabilization activities and changes in stream flow is strongly related to the degree to which the species is tied to riparian habitats. Of birds, the 13 species that are riparian obligates are the most vulnerable to bank stabilization activities. Belted Kingfishers would suffer if fish populations decline. Harlequin Ducks, Spotted Sandpipers, and American Dippers would be negatively influenced by changes in stream and bank morphology, especially the loss of shallow water and braided channels. Willow Flycatchers, Redeyed Vireos, Yellow Warblers, American Redstarts, Northern Waterthrushes, Common Yellowthroats, Wilson's Warblers, Song Sparrows, and Lincoln's Sparrows would be negatively affected if stream flow changes resulted in eventual reductions in the extent of shrub understocy. Species that are affected by changes in fish populations and stream morphology would suffer more rapid changes than species affected primarily by changes in riparian vegetation (either understory or trees), which would occur over a much longer period of time. Four amphibian species, three reptile species, and one mammal species are highly vulnerable to bank stabilization activities. Tiger salamanders, boreal toads, western chorus frogs, spotted frogs, rubber boas, racers, western garter snakes, and water shrews are expected to respond primarily to alterations in stream and bank morphology and the loss of still water for amphibian breeding.