Raptors such as owls don't always have it easy just because they are on top of the food chain. Smaller birds attack and pester owls caught flying in the open or roosting. Many types of birds may join the owl assault, which is known as mobbing. Songbirds most commonly attack owls, but birds as large as crows and as small as hummingbirds join in, also.
The harassment that occurs during mobbing usually consists of repeated dives as well as loud vocal calls designed to alert others to the owl's presence. Sometimes birds physically attack, plucking at the owl's eyes and feathers or clawing at its body. Owls are seldom hurt by these attacks and seem to ignore the mobbing behavior of other birds.