by Jerry Altermatt, Cody Region Terrestrial Habitat Biologist
CODY - If you’ve hunted the Yellowtail Wildlife Habitat Management Area in the last few years, you’ll have noticed a lot fewer Russian olive trees; a fact that many hunters are expressing concern about.
The Wyoming Game and Fish Department along with other partners began removing the invasive trees in 2006 and have treated over 1,500 acres on the Yellowtail WHMA and surrounding private lands. In the next two years, we will treat an additional 500 acres, completing mature Russian olive removal from the Shoshone River bottom lands from the bridge on Highway 37 to Big Horn Lake. The goal of the treatments is to maintain or restore quality habitat for waterfowl, pheasants, turkeys, and other wildlife.
Although Russian olive is listed as a noxious weed by the state, many hunters oppose removal of the plant because of its perceived value to wildlife. Many hunters correctly point out that game birds forage on the berries and deer utilize the cover that the trees provide. However, the ecological costs of unchecked Russian olive expansion far outweigh any benefits the plant may provide for wildlife.
Originally introduced as a shelter belt tree, Russian olive is an aggressive invader from Eurasia that is remarkably good at competing for sunlight, water, and nutrients. Like many introduced plants, it has few natural controls and quickly dominates the plant communities in areas along streams and rivers called riparian areas. At the early stages of Russian olive invasion, the few scattered trees have little effect on or, in some cases, actually improve habitat for some wildlife. However, that scenario is short-lived. In most riparian areas, Russian olive soon creates an impenetrable thicket that eliminates native plants and reduces the overall quality of wildlife habitat. Most wildlife require a variety of habitat types to meet their daily or seasonal needs. Pheasants, for example, may use dense shrub and tree cover for winter cover, but generally avoid these areas during other times. Pheasants particularly avoid areas with trees when selecting areas for nests because the trees provide perches for magpies and other aerial predators.
Highly productive and diverse riparian areas such as those found on the Yellowtail WHMA generally have adequate food resources for upland birds and waterfowl without Russian olive; it is quality nesting cover that is limiting. Whatever food benefit provided by Russian olive is negated by the reduction in quality nesting cover and inhibited production and diversity of vegetation. The cover needed by birds that is provided by Russian olive can be met by native trees and shrubs that Russian olive has replaced.
Hunters often suggest that we limit our treatments of Russian olive to provide patches Russian olive mixed with open areas. On the surface, it seems logical, but the approach is practically and economically infeasible. Treating mature Russian olive infestations is labor intensive and expensive. However, once these mature, seed-producing trees are removed, the cost of maintaining the areas free of Russian olive is minimal if done every three to four years.
Maintaining the above suggested scenario would entail frequent treatments of mature stands while at the same time a substantial and endless effort to maintain open areas in the presence of a constant seed source. Few land management agencies or funding partners have the means to finance that type of management.
(Contact: Cody Regional Office (307) 527-7125)