A recent entry described one of the fledglings being chased by crows. It is actually very common for birds of prey to be harassed by crows. Crows will mob birds of prey and try to chase them from the area. This is a defensive technique--they know that the tables could turn and that given the chance many birds of prey would turn around and prey upon them or their young. Some people wonder whether the crows aren't jeopardizing themselves by getting so close to the hawks. The answer is "no"---as long as the crows know where the hawk is, they can outmaneuver the hawks and get away. There is also safety in numbers. The "mobbing" aspect of crow harassment confuses the hawks and makes it very difficult to be aggressive.
The harassment can be quite dramatic with sometimes dozens of crows flying around, cawing and dive bombing the birds of prey. They will follow the hawk for perch to perch until it departs altogether. It can be quite a ruckus. It is often east to find hawks by listening for squawking crows. Crows are not alone in this type of behavior. Many bird species, even very small ones will try to drive predators from the area by harassment and mobbing behavior.
I always tell people who come out to watch us release rehabilitated birds of prey that the bird is likely to get harassed by crows as soon as we set it free, Crows have a knack for finding birds of prey that are discombobulated such as a hawk that has just been released back to the wild.It can be completely silent when you first let them go...and then a few seconds later you hear the first "caw"...and within minutes there are dozens of crows flying in from all directions to join into the fray.
There is no need to worry about the hawks however. This mobbing behavior is really just an annoyance. The crows usually keep their distance and are satisfied when the hawk leaves.
A friend of mine once told me a story of watching a lone crow harassing a red-tail off a fence post. The crow flew up beside it and began "cawing" from a few feet away. This went on for quite some tome until the hawk lazily lifted off and began circling up in to the sky. The crow followed and the two climbing birds eventually grew to be dots in the sky and the crow calls became fainter and fainter. Finally he lost sight of them altogether. A few minutes later the crow drifted back dwon alone and landed on the same fence post. My friend watched wondering what had become of the hawk when suddenly the red-tail cam hurtling down out of the sky and ripped the crow of the fence post. The hawk took his tormentor to a nearby perch and proceeded to pluck and eat his capture. Turnabout is fair play!