Loess Hills - Biology

Biology

The Loess Hills have abundant oak-hickory hardwood forests and some of the last remaining stands of prairie grass in the region. The invasion of prairie and oak savanna areas by woodland species such as red cedar (not native to the Hills) is threatening the stability of the fragile soils, as well as diminishing the native ecosystems found there. The areas of native prairie comprise big bluestem and little bluestem, Indian grass, sideoats grama and forbs such as yucca, pasque flower and lead plant (false indigo). Many of the prairie species found in the Loess Hills are outside of their normal range of distribution, with plants like spiny-leafed yucca and prickly pear cactus being more common further west, in the Sand Hills of central Nebraska. In 1984, a previously undiscovered fern, the Prairie Moonwort, was discovered in the Hills and is thought to be endemic to the Hills.

Common fauna of the modern Loess Hills include white-tail deer, coyote, wild turkey, badger, bobcat, red and gray fox, ringneck pheasant, bobwhite, and red-tailed hawk, some of which were introduced or encouraged by Euro-American settlers. Woodland species are also on the rise in the Loess Hills as the suppression of fire has led to an increase in habitat for forest-dwelling species. Fauna more typical of the pre-settlement Loess Hills, such as the prairie rattlesnake, great plains skink, plains pocket mouse, ornate box turtle and spadefoot toad, are becoming rare and even endangered due to habitat fragmentation as a result of increased development and suppression of fire in prairie remnants and oak savannas. Species such as bobcat have been rebounding, and mountain lions have been recorded in Southwest Iowa in the last decade. Historically, fauna also included American bison, prairie chicken, mule deer, elk, and gray wolf; these were extirpated by the late-nineteenth century.

The Missouri River valley had historically been a major migration corridor for birds, however, the channelization of the river and destruction of wetlands has led to a marked decline. The corridor still boasts one of the best areas to view raptor migrations on the continent. As air masses move off the Great Plains, they sink into the Missouri River valley. The prevailing winds across the floodplain then hit the sharp rise of the Loess Hills, creating thermal updrafts that raptors use to make their way to and from breeding grounds. Raptors can often be viewed forming "kettles," where many birds will create a funnel-like formation as they utilize the same thermal. Typical species found during the months from September to December include red-tailed hawk, sharp-shinned hawk, peregrine falcon, ferruginous hawk, Swainson's hawk, Cooper's Hawk, Osprey, Northern Harrier, American Kestrel, and Bald Eagle. In all, 20 species of raptor have been identified in a single season since the Hitchcock Nature Center HawkWatch started, with a record count of 16,000 birds in one season in 2005.

Broken Kettle Grasslands in the northern Loess Hills is home to Iowa's only population of nesting Black-billed Magpie.