Crescent Island is on the Columbia River above McNary Dam near the Town of Wallula (WA), and is owned and managed by the U.S. Fish and Wildlife Service as part of McNary National Wildlife Refuge. Crescent Island is artificial and was created from dredged materials in 1985 as mitigation for waterfowl nesting habitat lost during construction of the Wallula pulp mill; today it consists of ca. 7.5 acres with a mix of dense upland shrub habitat (island interior) and bare ground (island periphery). Caspian terns have nested on Crescent Island since shortly after the island was built. In 2001 the Caspian tern colony consisted of over 650 nesting pairs, but has steadily declined to ca 350 breeding pairs in 2009. The area used by nesting terns is small (0.17 acres) compared to the much larger area used by nesting California gulls, which use the area immediately adjacent to the tern colony and around the island’s periphery. About 6,500 pairs of California gulls nested on Crescent Island in 2009. The presence of the large gull colony on Crescent Island seems to limit the area used by the Caspian tern colony. Black-crowned night-herons and great blue herons nest in trees in the island's interior.
