I've crossposted this to !crows@lemmy.ml since others might be interested there. Thanks.

Crows vs. Owls: Enemies Ordained by Nature

Generally speaking, owls are nocturnal, crows diurnal - so that in the normal course of events they do not encounter each other. Occasionally, however, for reasons that are usually bad and certainly indicate trouble, their paths will cross.

Crows will harass, peck, annoy and mob an owl, sometimes to the death, if they discover one in the daylight. A roosting owl discovered during the day will be brutalized and occasionally killed by a mob of angry crows. I have seen a Barn Owl flushed from its roost by eager birders from a grove of cedars along the shoreline. It was quickly mobbed by crows and unable to return to shelter. The bird was attacked mercilessly by an ever increasing mob until they managed to drive it over the ocean and into the water.

Like hyenas and lions, owls and crows are destined to not get along. Lest you think the owl never wins, that is far from the case. A number of years ago I got to inspect a crow roost on the mainland that had been predated by a Great Horned Owl. The reason the identity of the predator was known was because there were 9 dead crows on the ground in perfect condition except that the top of their heads were gone and the brains eaten. This is the signature of the Great Horned Owl: completely in charge in the night. The roosting crows were easy targets for this most powerful of North American owls.

Please don’t disturb a roosting owl in the daytime - their lives depend on it.

Owls vs Crows: Brilliant Birds Battle

Though seeing a crow on its own is fairly common, with one call a single crow can summon the entirety of its flock. Crows are also highly intelligent, and each generation passes on knowledge. Crows have a long memory, and their high intelligence and ability to communicate with each other give them long memories. A crow can retain information and understands cause and effect. Crows live and travel in large groups, and each crow carries information from generation to generation. Even without ever seeing an owl, a murderer of crows knows instantly that owls are serious enemies! Crows attack owls on sight, knowing them as a serious threat that needs to be eliminated!

In addition to their astounding teamwork, crows are also quite smart and are one of the few animals that have mastered cause and effect. In fact, recent studies show that crows can use tools! Crows pass information from generation to generation and have long memories. A crow can remember specific animals and people they encountered up to five years prior as a threat.

This generational memory and understanding of cause-and-effect cause crow to attack owls during the day. Owls are vulnerable in daylight, and a murder of crows will mob an owl to prevent them from sleeping. Experts believe that this is an attempt to chase the larger predator out of the habitat to protect hatchlings. One crow will see an owl and call out to others to come to deal with the threat.

Crows vs Owls: What's Going On?

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 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.

This link has the most info and some videos showing mobbing behavior. Click through this one if you want more info.

Also discusses nest stealing which is an interesting subject also.

Why Do Crows Attack Owls? (Chasing & Mobbing Behaviors)

Have you ever noticed when you hear a group of crows cawing & making an awful racket in the woods, there’s often an owl at the center of those mobbing birds? It’s a pretty amazing thing to see!

In fact, if you know to listen for these crow mobbing calls, it’s one of the easiest ways to find owls in the woods.

But it also brings up the question of why crows attack them so intensely?

As a general rule, crows attack owls to reduce their risk of predation. Owls do sometimes eat crows and they frequently have overlapping nest habitats which puts them in close proximity.

However, if you watch this behavior for long enough it becomes apparent that crows are expending an incredible amount of energy attacking owls.

It also sometimes seems like they’re putting themselves at risk by coming so close to a dangerous predator, and yet the owls don’t really seem to react all that aggressively.

Mobbing looks like a group of birds all crowding around the danger, calling & even dive-bombing it. If the owl flies away, mobbing crows will often pursue and chase the target in a dramatic aerial battle.

So then why do crows care so much about owls?

Well, it’s a bit of a chicken and egg situation because given the right opportunity an owl certainly would eat a crow!

However, it’s very likely that part of the reason why crows don’t get eaten more often is because this mobbing, chasing & attacking strategy is such an effective defence.

There’s simply no way of knowing how often owls would hunt crows if they weren’t being pre-emptively attacked.

Slightly off-topic, but I have noticed full on wars going on between crows and seagulls. Might be just that crows are warmongers?