Four species of owls, Great Horned (Bubo virginianus), Long-eared ( Asio otus), Burrowing (Speotyto cunicularia), and Barn (Tyto alba), which occur together on the short-grass prairie and farmland of north-central Colorado, were selected for a study of feeding ecology. The purpose of this study was to assess the overlap in foods of the four owls and to examine feeding mechanisms which allow them to coexist. Primary objectives were (1) to analyze and compare the food habits of each owl species considering frequency of occurrence of prey species and biomass contributed by each prey species, and (2) to describe and evaluate the primary factors involved in capture of prey by the four owl species. Few studies have been attempted in relation to the feeding of owls in this geographic area and none was a long-term study. Reed (1957) examined Barn Owl pellets from Larimer County, and Kelso (1938) and Hamilton (1941) noted Burrowing Owl foods in the Denver area. Catlett et al. (1958) studied foods of Long-eared Owls near Boulder, and Long and Kerfoot (1963) listed Great Horned Owl foods from east-central Wyoming. Most abundant of these owls is the Great Horned. This species, a permanent resident of the area, is extremely versatile in both its nesting and feeding, allowing it to utilize a wide variety of habitats. The Burrowing Owl is abundant during summer. Burrowing Owls are restricted to open lands with available nesting and roosting sites in abandoned mammal burrows, chiefly those of black-tailed prairie dogs (Cynomys ludovicianus). Arriving by mid-April, they spend about 6 months in the area before returning south in midto late October. Barn Owls are less common. Northcentral Colorado is close to the northern limits of this species' range and some may move south in winter. However, some remain through the year. Rock cliffs or ditch banks are sought for nesting and roosting by Barn Owls. Long-eared Owls are also uncommon. They appear to be nomadic-there one year and gone the next. Low, dense coniferous or deciduous trees attract them for nesting and roosting. A number of other vertebrate predators are present in this area whose diets may overlap with those of the four owl species. Other avian predators are the Golden Eagle (Aquila chrysaetos), Marsh Hawk (Circus cyaneus), Red-tailed Hawk (Buteo jamaicensis), Swainson's Hawk (B. swainsoni), Rough-legged Hawk (B. lagopus), Ferruginous Hawk (B. regalis), American Kestrel (Falco sparverius), Prairie Falcon (F. mexicanus), and Loggerhead Shrike (Lanius ludovicianus). Mammalian predators include red fox (Vulpes fulva), coyote (Canis latrans), raccoon (Procyon lotor), American badger (Taxidea taxus), striped skunk (Mephitis mephitis), and longtailed weasel (Mustela frenata). The more abundant reptilian predators are the gopher snake (Pituophus melanoleucus) and prairie rattlesnake (Crotalus viridis). The research was carried out from Decem-