Approximately 291 species of birds nest or migrate through Effigy Mounds National Monument. The wild turkey once extirpated is now nesting on the Monument. The Yellow River floodplain has been identified as one of 12 nesting sites of the red-shouldered hawk in the state of Iowa.
The Mississippi River backwaters provide habitat for many interesting plants and animals. The majestic bald eagle nest on islands and feed on fish they pull from the river with their powerful talons. Hundreds of bald eagles winter along this stretch of the river. In the coldest winters, when open water is scarce, eagles move further down the river in search of food. Colonies of great blue heron, great egrets and double crested cormorants nest in trees. The rookeries, as these nest sites are called, are noisy places in spring with young fledglings being fed by their parents.
The prothonotary warbler lives in the floodplain forest along the sloughs where its loud call can be heard on early summer mornings. The warbler nests in woodpecker holes left in dead snags overhanging or near the water. Naturalist Aldo Leopold called the prothonotary warbler the crown jewel of the disease ridden woodlot. The males bright yellow on the head and breast and bluish wings are a sharp contrast to the green of the forest. A small warbler of the forest canopy found here is the cerulean. The cerulean warbler usually stays high in the trees, but its high pitched buzzy call can be heard in early summer while they forage hidden by leaves in the canopy. A special virtue of warbler viewing is patience.
The bluffs and hills along the Mississippi River provide a corridor for migratory species. Each spring and fall, neotropical birds use the forested bluffs for feeding and resting stopovers. Migrating raptors use the thermals rising from the bluffs on their biannual flight to and from nesting and wintering sites along the Mississippi Flyway, one of the major migratory bird routes in the country.
In the summers of 1998-99, nineteen peregrine falcons were released at Effigy Mounds by Raptor Resource Center of Bluffton, Iowa. Peregrine falcons were released from hacking boxes located at Hanging Rock. The plan was to release captive-bred birds on the cliffs of the Mississippi River and have them imprint on the limestone bluffs overlooking the river. It is hoped that some of the birds will return to the cliffs and set up territories and nest among the ancient sites along the river.
