In the progression of seasons, animal abundance within the Ozark Mountains ebbs and flows as animals migrate in and out of the oak-hickory ecosystem that exists within the rough hills and valleys that create the Buffalo National River. With the coming of spring, fish are actively migrating up the river corridor into tributaries, and songbirds are arriving from far off places, filling the forest canopy with movement and song. Wildlife observers have recorded 55 species of mammals, 250 species of birds, and 59 species of fish, along with a multitude of reptiles, amphibians, insects and other invertebrates. Several of these species have restricted habitat preferences, which are only found within the hills and hollows of the Boston and Springfield Plateau ecoregions; many of these habitats are found within the boundary of the park.