Endangered butterfly. Fender's blue butterfly was thought to be extinct from 1940 until the late 1980's when biologists discovered a few remaining populations in the Willamette Valley. It prefers native upland prairies with abundant flowering plants that provide food for larvae and adults. Kincaid's lupine is its primary larval host plant. The open structure of prairies is just as important to this butterfly as all the threatened and endangered prairie wildflowers. Refuge staff maintain these habitats through burns and mowing. The largest known population of this butterfly is found on Baskett Slough's Baskett Butte. Fender's blue are active as adults only a short period of their lives, spending much of their lifespan in larval and pupal stages. To catch their brief period of flight, visit Baskett Butte from mid May to early June.

Endangered wildflower. The Willamette daisy typically occurs in upland prairie and oak savanna habitats with little to no shrub cover. These habitats require periodic disturbances that prevent the encroachment of trees and shrubs to maintain the open landscape, thus suppression of these disturbances has led to habitat loss and a decline in the daisy populations. The refuge uses prescribed fire and mowing to prevent this encroachment and boosts population numbers with supplemental plantings and the use of herbicides on non-native competitors. A significant population of this endangered flower is found in the native upland savanna of Baskett Slough.

Threatened passerine. The streaked horned lark was first listed under the Endangered Species Act in 2013, and critical habitat has been designated on all three Willamette Valley Complex Refuges. The habitat favored by the lark is characterized by wide open spaces with few trees and shrubs. The designated habitat areas are managed by the Service for streaked horned lark use through reintegration of natural disturbance processes, such as fires, which prevent large shrubs from encroaching.

Threatened prairie wildflower. Kincaid's lupine occurs in upland prairies and oak savanna habitats with little to no shrub cover. Habitat loss and lack of regular disturbances (which prevent the encroachment of trees and shrubs) have caused populations of the flower to dramatically decline. The protection of this plant species is not only important for its own survival, but it is a vital element in the survival of the endangered Fender's blue butterfly. Kincaid's lupine is one of Fender's blue butterfly's primary larval host plants. Refuge staff utilize prescribed fire, mowing, and herbicide treatment of non-native plants to maintain the open habitat the flower requires and supports its populations through plantings. Some Kincaid's lupine occurs on Baskett Butte, though much of it has hybridized with a closely related plant, spurred lupine. Spurred lupine and the Kincaid's-spurred hybrids also serve as host plants for Fender's blue.

Threatened wildflower. Nelson's checker-mallow typically occurs in wet prairies and floodplains of the Willamette Valley and Coast Range. Its habitat is threatened much like that of the Willamette Daisy due to the suppression and elimination of natural disturbances, resulting in the encroachment of woody vegetation. Refuge staff is working to recover this flower through supplemental plantings and habitat management techniques such as mowing and prescribed fire.

Threatened prairie wildflower. Golden paintbrush typically occurs in upland prairie habitats with flat or mounded topography. Completely extirpated from its historic range in Oregon by 1983, the paintbrush was reintroduced to this area through the Golden Paintbrush Recovery Plan. Biologists on Baskett Slough actively work to boost the golden paintbrush populations through supplemental plantings, prescribed burns and mowing on refuge prairies. Aside from the Willamette Valley, golden paintbrush has been found in Washington and British Columbia in the Puget Sound area. Over half of the eleven sites found there occur on Whidbey, San Juan and Lopez Islands.