The link above is for a Blog by wildlife photographer Galen Leeds Photography .
The reason I posted this link is that Galen talks about seeing a pair of red tailed hawks copulating and, then without warning, here comes a Peregrine falcon at a tremendouse speed and smashes into the pair of hawks, separating them.
He has managed to capture the event on camera, and is asking if anyone has any knowledge of similar activity.
Galen lives and works in California and appears to spend most of his photography shooting time in a Kayak!
I've heard many accounts of Peregrines mobbing and having a go at larger raptors when they get the chance - driving off a potential threat/competition. I'm sure the Peregrine didn't particularly care what the Red-tails were doing at the time :)