Barred owl population filled the niche of a spotted owl and the rapid expansion of the barred owl into the range of the spotted owl occurred. The barred owls are a little bit larger, more aggressive and have a wider variety of prey species than spotted owls. Also, barred owls nest more often and successfully, thus producing more young than do spotted owls. This gives barred owls a competitive advantage over spotted owls and as a result, spotted owl populations are rapidly declining in many areas.