Harper Island is the only sizable island in Sprague Lake and is located near the southwestern end of the lake. Sprague Lake is between the towns of Ritzville and Sprague in east-central Washington, and is located about 48 km from the nearest section of the Snake River. Harper Island is a steep-sided, rocky island approximately 10 acres in size and covered by upland shrub habitat and bare rock. Caspian terns were first found nesting on Harper Island in 1997 (if not earlier) and in 1999 the colony was estimated to consist of about 50 breeding pairs. Since then the colony has declined in size with only about 4 breeding pairs attempting to nest on Harper Island in 2009, and no nesting attempts produced any young. The island is also home to a small double-crested cormorant colony (42 breeding pairs) and a large California/ring-billed gull colony (ca. 6,300 breeding pairs in 2009).
