From Birder's World Magazine's Website
Large hawks prey on small mammals. The Red-tailed Hawk feeds on rodents and rabbits but also catches larger animals, including pheasants, hares, and jackrabbits. Likewise, Ferruginous and Harris's Hawks chase rabbits, rodents, and ground squirrels. Swainson's Hawks eat mice and large insects.
Of the prey items I've mentioned, jackrabbits are the heaviest. They weigh no more than 10 pounds, less than your pet. Since a small dog could look about the same size as a hawk's usual prey, however, it's possible that a hungry raptor might at least attempt to capture the dog, injuring it in the process.
Be more cautious, though, about leaving your dog outdoors at night. Great Horned Owls are powerful hunters that eat a wide variety of prey, including raccoons, porcupines, and house cats - all of which can weigh as much as your pet.
Recently in Great Britain, a Eurasian Eagle-Owl made headlines when it repeatedly attacked at least five dogs. The owner of one of the dogs, a miniature wire-haired dachshund, said, "It is very frightening for Heidi to have this giant bird trying to eat her all the time. I have no doubt that it wants to make her into its next meal. I guess Heidi looks like a rabbit or a tasty snack." A falconer captured the bird, which was believed to have escaped from an aviary.
Please read comments below since I have added a lot more info on this problem with links to even more information. Protect your pet with knowledge to keep it alive.
Have a bird question? Ask it at Birder's World.