The other week while I was out hiking and birding with friends, we saw a great horned owl fly silently through a clearing and disappear back into the woods. I was screened by trees in the forest, but could see the owl's big head (my friend calls them jughead as a result) and broad wings, leaving no doubt what it was. My friends and I quickly turned around and tried to find it in the trees. We didn't need to do so.

As we walked a few paces back in the soft, spring woods, an American crow began to caw! loudly just ahead. The owl's flight had been spotted. We hadn't heard crows calling before we saw the owl, but the bird may well have been chased there initially. The lone crow calling was not alone for long. Soon a few more crows began cawing – anxiously telling everything in the woods they had found a great horned owl. Other crows began to arrive – from where we couldn't say, but the message was being heard far and wide and every crow within earshot wanted a piece of the action.

Because we were in the woods, we couldn't see the owl. We could only ascertain its position by listening to the crows – the shadows of which passed above the trees. Suddenly the crows' cawing hit a deafening fever pitch, and we knew the owl was on the move. We ducked and looked around trees to catch a glimpse of it in flight. The owl was gaining an entourage of crows at this point, and from the sound of it hadn't flown far – just into an adjacent wooded patch.

We continued searching for it, and found a large group of crows sitting in the trees calling loudly. We owl was clearly in a pine tree and after some maneuvering, we could just make it out through the branches. I tried to ready my camera for shots of the scene when with the raucous chorus as its heels, the owl dipped out of the tree, flew behind a screen of trees, and landed again a short distance away – again hidden from view. It was trying to hide from the crows, but doing a poor job of it.

Crows were flying in to join the chase as if every crow in the neighborhood had nothing better to do than to wait to hear about a great horned owl which needed to be run out of town. They were streaming in from all directions and soon there were 50 or 60 crows scattered throughout the trees and air and all positively screaming at the owl.

And while to our eyes it may appear that crows are perhaps being mean-spirited or just having fun at the expense of the owl, their behavior is not without its advantages. Great horned owls are excellent nocturnal predators, and they catch and eat a variety of prey items, a list which includes crows sitting on their nests or roosts at night. During the day, however, the crows have the upper hand on the owl, which they press home by flooding it with numbers – hounding the owl relentlessly until it finally gives the mob the slip.

Crows harass most large species of raptors or owls. After all, any predatory bird could theoretically pose a threat. We've all seen them harass species such as red-tailed hawks or barred owls, among others. But their efforts with other species seem mild compared to the energy which they direct against great horned owls. There is an urgency in their constant mobbing and cawing, which for lack of a better description, seems to stem from hatred. That word goes too far and may anthropomorphize things a bit, but seeing the crows mob the great horned with such ferocity was an amazing contrast to how little crows seemed to care about the great gray owls I observed sitting in the open this winter. Crows are intelligent birds, and they appear able to discern which threats are the greatest. After all, despite their size, great gray owls do not pose nearly as much threat to crows as great horned owls.

From the perspective of the harried owl, this intelligence may be a total nuisance, and we chuckled to ourselves that the owl was counting the minutes until darkness fell and the tables would be turned in its favor. Our owl barely made itself visible to me and my camera in a vain attempt to hide from the harassing crows which sat around defaming its very existence. Finally its patience gave in, and the owl flew again, with better than 60 crows yelling in its train. This time it flew a long way off, and we heard the din of the crow chorus slowly disappear into the distance. We never relocated it. It was going to be a long time before that owl had any peace.