Wildlife on Conservation Reserve Program lands and native shrubsteppe in Washington: 2003 Progress Report

The Conservation Reserve Program (CRP) is currently the only large-scale effort to restore habitat that may be used by grassland and shrubsteppe wildlife in the Columbia River Basin. Administered by the US Department of Agriculture, this voluntary program pays farmers to take agricultural lands out of production to achieve conservation objectives including reducing soil erosion and providing wildlife habitat. In Washington, over 1 million acres (405,000 ha) of converted farmland has been planted to non-native grasses and to native grasses, forbs and shrubs under the CRP. In 2003 we began a study to evaluate the potential role of CRP in the long-term conservation of obligate grassland and shrubsteppe wildlife in the Columbia River Basin. We established 48 study sites in CRP fields of varying age and landscape contexts and in extant shrubsteppe communities. From April-October 2003 we surveyed for birds, herptiles, and small mammals and we examined reproductive parameters of selected bird species. Preliminary data from the first year of study show a bird community dominated by grassland species in CRP sites. This pattern was not unexpected and reflects the structure of the vegetation and its similarity to native steppe communities. Three shrubsteppe-obligate passerines (Sage Sparrow, Sage Thrasher, and Brewer’s Sparrow) also occurred in CRP stands, with Brewer’s Sparrows occurring in considerable numbers. Highest numbers of all 3 species were recorded in old CRP sites in shrubsteppe-dominated landscapes, likely reflecting the increased occurrence and height of big sagebrush in these old CRP stands. Nesting data confirmed that these shrubsteppe-obligate birds were breeding successfully on some CRP sites, with numbers of Brewer’s Sparrow nests found in some CRP sites approaching that found in extant shrubsteppe. Most color-banded males successfully paired, and a preliminary look at the nesting success data suggests that nests in CRP fields were at least as successful as those in shrubsteppe sites. Surveys for herptiles in 2003 revealed a greater number and diversity in extant shrubsteppe embedded within shrubsteppe landscapes than in other site types. Shrubsteppe sites in agricultural landscapes and old CRP plots embedded in shrubsteppe landscapes supported some, but not all of the species locally present. New CRP plots within either landscape and old CRP plots in agricultural landscapes were depauperate of herptiles. We captured >10 species of small mammals during approx. 23,000 trap nights in September and October. Three species, the deer mouse, Great Basin pocket mouse, and western harvest mouse made up 90% of captures. Other species captured included the least chipmunk, sagebrush vole, montane vole, long-tailed vole, northern pocket gopher, Merriam’s shrew, and vagrant shrew. Three rodents (deer mouse, western harvest mouse, and sagebrush vole) showed trends toward higher average relative abundance in CRP fields than on shrubsteppe sites. The Great Basin pocket mouse had similar captures across all site types whereas least chipmunks were captured mainly in shrubsteppe habitats. Field data collection for all 3 species groups will be repeated in 2004. In addition, the vegetation at all 48 study sites will be characterized so that we may further define the habitat relationships of wildlife in CRP and shrubsteppe communities. A third year of data collection in 2005 would be desirable but is contingent on additional funding.

Results presented above are preliminary: more detailed analysis and inclusion of additional data in 2004 may reveal different trends