In the last century, despite often roosting in human-built structures, Barn Owls have declined in the upper Midwest. The species is now considered to be accidental in Minnesota. A number of factors have contributed to this situation. First, grasslands, which the Barn Owls favor, have often been replaced by cropland or urban development. Second, you might think that a bird that roosts in barns and other out-buildings would not be in trouble--but these types of structures are slowly disappearing from the farmlands as barns collapse and large agribusinesses take over family farms. Third, Barn Owls are often roadkill. In some areas, the building of major highways has caused the extinction of local Barn Owls.
I took this photograph of a young Barn Owl near Pierre, South Dakota. There Barn Owls are relatively common and can be seen if you know where to look. These young birds were in a burrow-nest in a cliff-side along the Missouri River. Near Pierre, I have also seen Barn Owls under local highway bridges and in structures on top of the Oahe Dam. Where the owls are still common, populations depend on nesting sites (either human-made or natural) and high rodent populations.