Cats and mice, spiders and flies, and wolves and elk are all animals that we think of being arch-enemies of one another. But we can add another pair to our list: owls and crows. Anytime crows see an owl flying around they will harass it continually to try and keep the owl awake and annoyed. Although this seems cruel, the crows may not actually be the villains of our story, indeed it is somewhat unclear who the true villain is. Regardless of which animal you support, the crow vs owl story is an interesting one to consider.
During the day, the crows will bother the owls that are perched somewhere sleeping, and at night the tables turn when the owls come out to hunt. Generally, owls do not predate crows. However, some of the larger breeds of owl (such as the Great-Horned Owl) will opportunistically hunt young crows if they come upon them. While there does not appear to be a definitive answer among the scientific community about why crows expend energy mobbing owls, at any time other than during the breeding season when they are protecting their young, the prevailing theory is that crows have an innate dislike of owls and use their daylight advantage to torment their largest predator. Numerous studies have shown that crows are able to identify things that have attempted to harm them and have the ability to share that knowledge with the rest of the flock. Thus, if an owl has taken a pass at, or successfully killed a crow, the rest of the flock will likely learn about it and take the next opportunity to exact revenge, even if the attack did not happen recently. Some studies suggest that this mobbing behavior may reduce the likelihood of an owl killing a crow the next time it comes across one, which is a potential benefit to mobbing any owl a crow sees. The next time you hear a bunch of crows causing a tremendous ruckus on campus or in the Arboretum, they might be mobbing a tired owl trying to get some sleep.
This time of year is particularly important for owls because many of the owls in Minnesota are currently in their mating seasons. Generally speaking, owls are monogamous and will stay with their mate for at least the length of the breeding season. During this time they get very protective of their territory and will let out calls to make sure other owls stay away. Since they are particularly vocal in the spring, this is your chance to get into the Arboretum and try to hear some owl calls. However, if you do come across a sleeping owl in the Arb, try not to disturb it. If owls have to leave their perch, they may be driven away and kept awake by the crows, which could be detrimental to their breeding season.
If the owls of Minnesota have piqued your interest, the Minnesota DNR website and Arboretum website are both excellent resources. Additionally, The Owl Pages is a good place to go to learn about owls in a broader context.
Alex Bynum ’18 for the Cole Student Naturalists
Photo credits: On page- Dan Tallman (Great Horned Owl), teaser- Eric Johnson (Barred Owl)