The female Barn Owl tends to be more spotted on the breast than the male. These spots may act as a stimulus to the male, indicating the quality of the female. If a female's spots were experimentally removed, her mate fed their nestlings at a lower rate than if the spots were left alone.
Up to 46 different races of the Barn Owl have been described worldwide. The North American form is the largest, weighing more than twice as much as the smallest race from the Galapagos Islands.
The Barn Owl is one of the few bird species with the female showier than the male. The female has a more reddish chest that is more heavily spotted. The spots may signal to a potential mate the quality of the female. Heavily spotted females get fewer parasitic flies and may be more resistant to parasites and diseases.
The Barn Owl has excellent low-light vision, and can easily find prey at night by sight. But its ability to locate prey by sound alone is the best of any animal that has ever been tested. It can catch mice in complete darkness in the lab, or hidden by vegetation or snow out in the real world.