The U.S. Fish and Wildlife Service and partner agencies manage for migratory birds based on specific migratory routes or flyways within North America (Atlantic, Mississippi, Central, and Pacific). The migratory paths are influenced by geography, wind, and weather patterns. Refuges within the Theodore Roosevelt Complex are located in the Mississippi flyway. Over 800 species of migratory birds are protected under the Migratory Bird Treaty Act, which was one of the first environmental laws established in 1916. More than 225 species of migratory birds use the Complex, with 77 species breeding on Complex lands.
Mallards are the most abundant wintering waterfowl species, followed by gadwall, green-wing teal, pintails, and shovelers.
Wading bird rookeries exist on 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, and tricolored heron.
About 20 species of shorebirds use Morgan Brake NWRs, where moist-soil habitat is managed intensively. Shorebirds include the avocets, oystercatchers, phalaropes, plovers, sandpipers, stilts, snipes, and turnstones. They are usually small bodied with long thin bills. The differences in their bill lengths and shape allow the different shorebird species to forage for food within their habitat either on dry soil, mud, or in shallow water. Shorebird migration spans a great distance. During the spring, summer and fall migration, shorebirds rest and feed at stopover locations including refuges in the Theodore Roosevelt NWR Complex. Shorebirds eat a variety of invertebrate prey such as worms, insect larva, amphipods, copepods, crustaceans, and mollusks.
In 2013, black-necked stilts were documented nesting at Morgan Brake NWR. Previously, this species only utilized the refuge as a stopover location during migration. Black-necked stilts nest on the ground. They tend to build on surfaces above water, such as small islands, clumps of vegetation, or even, occasionally, floating mats of algae. Black-necked stilts are semi-colonial when nesting, and they participate en masse in anti-predator displays. The displays include one in which non-incubating birds fly up to mob predators, and one in which all birds encircle a predator, hop up and down, and flap their wings.
Marsh birds are a group of water birds including rails, bitterns, grebes, gallinules and snipe that typically inhabit dense, emergent wetlands. These species are known for their secretive nature; they are seldom seen or heard because they vocalize infrequently and prefer inaccessible wetland habitat. A large rail of freshwater marshes, the king rail has declined alarmingly in much of its range over the last 40 years. King rails utilize managed wetlands at Morgan Brake NWR. The species has been identified as a focal species by the U.S. Fish and Wildlife Service due to severe population declines in the northern, central and eastern parts of its range in North America.