MARS Monitoring Report October 2024: Great Horned Owl

By David Ryan, Monitoring & Outreach Coordinator

Knock knock. Who-hoo-oo-oo’s there? A Great Horned Owl (GHOW), Bubo virginianus.

While working on the Conboy Lake National Wildlife Refuge, my colleague and I were closely watched by this Great Horned Owl. Determining the sex of Great Horned Owls is difficult since there aren’t obvious differences in coloring between the sexes. Although females tend to be larger than males, this difference was not readily apparent to us in this situation. For some reason, we instinctively referred to this owl in the feminine but it may have been a male. She was very calm as she watched us from a closer range than I have ever been to a wild owl in my decades in the woods.

GHOW populations are considered stable per the IUCN Red List of Endangered Species. They are large owls 18-25 inches in length and can reach weights of over 5 pounds. They have distinctive ear tufts that give rise to their common name, and they possess a fairly distinct facial disk that helps direct sound waves to their ears. With eyes that are packed with rods for good night vision and soft feathers that allow for silent flight, Great Horned Owls are well adapted for nocturnal hunting but they will hunt during the day as well. To compensate for the fact that they are unable to move their very large eyes within the sockets, these owls are capable of turning their heads a full 180 degrees.

GHOW do not migrate annually and are usually permanent residents. For sound reasons, these owls are still protected under the Migratory Bird Treaty Act of 1918. They occupy a wide variety of habitats throughout North America and down through Central and South America. Preferred habitat includes a variety of open woodlands that hold ecosystems such as fields, wetlands, and pasture. My colleague and I were working in an open Ponderosa pine and Oregon white oak woodland close to meadows and wetlands, which was the textbook habitat for these magnificent birds.

Their diet is dominated by mammals such as squirrels, rabbits, gophers, and other rodents. They also feed on ducks, coots, and other waterfowl; but they are not above eating reptiles, amphibians, and insects. Owls can predate upon small livestock and domestic animals such as chickens, small dogs, and cats. The best defense is to create secure enclosures for domestic animals at risk of owl predations. Like other predators, owls can learn routines and patterns on a given property to increase hunting success. If you notice an owl regularly on your property, changing your patterns around pets and livestock can help reduce predation. Noise makers and scare devices can also reduce, but not necessarily eliminate losses. Check out WA Dept. of Fish & Wildlife for more information.