I got as close as I dared without disturbing her meal and watched her eat. You can see a nice bit of meat in her beak here. It is very likely that her mate brought her this snake. At this stage of the nesting season, he was bringing her food all the time. Keeping her well fed so she can produce eggs when the time comes.
Red-shouldered Hawk (Buteo lineatus)
Graham's Crayfish Snake (Regina grahamii)