More than 225 species of migratory birds use the Theodore Roosevelt Complex, which includes Hillside NWR, with 77 species breeding on Complex lands. Ten species with Partners-in-Flight “concern scores” of 20 or more are common or abundant, including prothonotary warbler, painted bunting, red-headed woodpecker, yellow-billed cuckoo, wood thrush, white-eyed vireo, yellow-breasted chat, Carolina chickadee, loggerhead shrike, and dickcissel. Mallards are the most abundant wintering waterfowl species, followed variously by gadwall, greenwing teal, pintails, and shovelers. Snow geese occupy Morgan Brake NWR and Yazoo NWR in large numbers during winter, with flocks sometimes exceeding 100,000 birds. Wood ducks and hooded mergansers are common nesters in the spring and summer, depending on the size of the nest box program on each refuge.
Wading bird rookeries exist on Yazoo, Hillside, and Morgan Brake NWRs. Nesting species include the great blue heron, great egret, snowy egret, little blue heron, cattle egret, black-crowned night heron, anhinga, tricolored heron, and, more recently, the double-crested cormorant. White ibis have occupied rookeries on Morgan Brake NWR in the past, but currently are the dominant species using a large rookery adjacent to Panther Swamp NWR.
About 20 species of shorebirds use the Complex, especially Yazoo and Morgan Brake NWRs, where moist-soil habitat is managed intensively. Some of the most numerous species are least sandpipers, pectoral sandpipers, lesser yellowlegs, and stilt sandpipers.