Definitely red-tailed hawk feathers. A peregrine is a very unlikely suspect... not very common, especially in rural areas.
Most times, red-tails will attach their prey with talons clenched... like fists. They swoop down and knock the prey out, instead of grabbing them and flying away immediately like you see in the movies. When they attack like this, they can sometimes stun themselves along with the prey. My theory is... Hawk attacked rabbit, knocked out rabbit, knocked itself out also, then scavenger predator ('yote, fox, coon, etc) came along and reaped the benefits.