Riparian (streamside) vegetation provides habitat for breeding, migrating, and overwintering birds, and is also critical to the quality of the in-stream habitat on which salmon fisheries and other aquatic species depend. In the western United States, riparian zones make up less than 0.5% of the total land area, yet they support the most diverse bird communities of any habitat type in arid and semi-arid regions. Riparian habitats are also highly imperiled due to human impacts, and now cover only a fraction of their former range. Their relative rarity on the landscape, yet high biodiversity, makes riparian zones one of the most important habitats for the conservation of birds and other wildlife in the West.
TRINITY RIVER RESTORATION
Since 2002, the Bureau of Reclamation’s Trinity River Restoration Program (TRRP) has been working to restore salmonid populations impacted by dams on the Trinity River in northern California. Restoration involves removing steep river banks where the river channel has become incised, lowering the floodplain, and reconnecting the riparian habitat to the river, for the benefit of both fish and terrestrial wildlife. Scientists at KBO have used a suite of focal bird species as ecological indicators, evaluating the health of streamside habitats as they were replanted with native vegetation following rehabilitation projects. KBO’s research built upon bird monitoring work initiated by the US Forest Service Redwood Sciences Laboratory, using twelve years of riparian and riverine bird surveys to track changes in the abundance and diversity of bird populations in the section of river affected by restoration activities. We also expanded the bird monitoring project in 2012-2016 by implementing new methods that provide more intensive measures of restoration response, such as whether birds are choosing territories in the recently restored riparian habitat and, if so, whether or not they are successfully fledging young. Our findings have shown that Song Sparrows, birds with the flexibility to colonize young riparian vegetation, are nesting in the recently restored areas as successfully as they are in areas of mature habitat. Other focal species may need more time for complex vegetation structure to develop before they occupy the regenerating floodplains in high numbers, but data indicate a trajectory toward success. Results will be used within the adaptive management framework to assess and improve the TRRP’s success in creating ecologically viable riparian habitat with high value for wildlife. Click here to view “report card” style summary of the progress of riparian restoration along the Trinity River.
SCOTT RIVER VALLEY BEAVER DAM ANALOGUES (BDAs)
In fall 2015, KBO started a partnership with the Scott River Watershed Council (SRWC) near Etna, CA, to monitor ecological changes resulting from the implementation of beaver dam analogues (BDAs) in the Scott River Valley. BDAs are woody structures built by people to mimic the beneficial effects of beaver dam impoundments, such as improving water retention and groundwater recharge, increasing base flows, and lengthening the time in summer when above-ground flows are present. Beaver dams can also expand the size and complexity of wetland and riparian areas, providing important habitat for birds and other wildlife, including endangered Coho salmon. Researchers at KBO recording the abundance and diversity of both the summer breeding and fall migrating bird communities to assess the effects of these restoration efforts. Past studies of beavers in New York and Arizona both showed that active beaver sites—and all of their associated habitat complexity—supported more species of birds than sites without beavers. Our preliminary surveys have found over 80 bird species using habitat near BDAs in the Scott River Valley. We will continue to monitor changes in bird communities using the BDA sites over time, as they continue to develop into more complex riparian and wetland habitats.
GOLD RAY DAM
KBO applied our model of using birds as ecological indicators to assess the effects of the removal of Gold Ray Dam on the Rogue River near Gold Hill, OR. Despite the number of planned dam removal projects in the U.S., effects of large-scale dam removal on in-stream and riparian habitats are not well-studied. The Gold Ray Dam project provided an opportunity to collect data so that we can better understand ecological changes that occur following dam removal and inform future planning efforts. The abundance of one bird species, Wrentit (Chamaea fasciata), declined in the wetland area previously maintained by the backwater from the dam. In this area, shrub and ground cover decreased following dam removal, possibly the result of eradication of non-native species. Overall bird community composition did not differ between controls and treatments either before or after dam removal, suggesting shrub and tree components of riparian habitat did not change in quantity or quality in the two years following dam removal. However, this is a very short-term time frame, and the longer-term effects are still unknown. As the ecosystem continues to recover, vegetation cover, bird abundance, and community composition will likely continue to respond over the next decade or more.
FOURMILE MEADOW RESTORATION
The Fourmile Creek and Harriman Springs Restoration Project is enhancing habitat on the west side of Upper Klamath Lake for the benefit of fish and birds. Lost River and shortnose suckers, redband trout, and migratory birds—such as Lincoln’s Sparrow, Song Sparrow, and Common Yellowthroat—are expected to respond positively to the restoration of a 400-acre wet meadow, three miles of forested riparian areas, and spawning habitat in Harriman Springs and at the mouth of Fourmile Creek.
Partnering with US Fish and Wildlife Service, US Forest Service, US Geological Survey, and others, KBO’s role in this project is to monitor birds as indicators of restoration success. In 2012 KBO completed our second year of post-restoration surveys during the breeding and fall migration seasons.