Complex sentence: Although this owl is often claimed to have exceptional night vision, its retina is no more sensitive than a human's, but its asymmetrically placed ears give the Tawny Owl excellent directional hearing.
Split into simpler sentences: Although this owl is often claimed to have exceptional night vision, its retina is no more sensitive than a human's. Rather, it is its asymmetrically placed ears that are key because they give the Tawny Owl excellent directional hearing.