European barn owls are slightly smaller than their North American cousins. Although they can grow up to 13 inches in height, they tend to weigh only 1 pound which helps them sustain long flights over fields as they look and listen to prey. The barn owl is highly adaptive to prey availability. For example, in Spain, the barn owl hunts mostly house mice, which in Austria, they have been known to catch bats. On a few occasions, they have been observed successfully catching fish.