Several years ago, while walking through a mature stand of Norway Spruce trees at dusk, I startled a large bird of prey with a kill. The bird was less than 10 meters in front of me, on a dead limb about 3 meters high. Even though it was nearly dark, I could see that it was a Great Horned Owl and also saw its large, dark-bodied kill plop to the ground as it made a hasty escape. The victim was a crow, and it had been decapitated.
The fact that owls eat crows is at least a partial explanation for the mobbing behavior of crows. Pity the roosting owl (or hawk) that is discovered by a flock of crows. The raucous harassment can be heard for hundreds of meters and is relentless, continuing until the raptor takes flight and is driven away.
On two occasions I’ve had the good fortune to see the interaction between a Snowy Owl and mobbing crows in daylight: last winter (“Mobbed” https://nicksnaturepics.wordpress.com/wp-admin/post.php?post=2038&action=edit) and again three days ago.
The reaction of crows to a white owl perched on the ground seems to be much less intense than expected, possibly because this is such an unusual and seldom seen raptor. These crows were fairly quiet and, after a feeble attempt to intimidate the Snowy, simply flew away. The owl appeared to be somewhat annoyed, but not alarmed; it never budged.
Photos by NB Hunter. © All Rights Reserved.