Live-prey testing
Raptor rehabbing is not for the squeamish. Hawks and owls are dangerous and often extremely temperamental. Even though we've had years of dealing with them, we still experience injuries (spouse was badly footed just this past fall.) Those of us who handle them have to accept their down sides. One of those down sides is food.
Since most raptors primarily eat rodents, we are obliged to provide a comparable diet. Different raptors need different sizes. Kestrels and screech owls take very small mice. Great horned owls take big rats. Some rehabbers raise their own mice, but most of us obtain them either from pet stores or research facilities because they are considered cleaner sources. There are also businesses that cater to rehabbers who sell quail, pheasant, chicks, etc. relatively cheap. It might help you to know most of us buy them, or get them donated, already dead and frozen like meat in a grocery store.
However.
One of the more unpleasant duties when dealing with raptors is something called live-prey testing. It comes at the end of a raptor's time with a rehabber, when a bird is about to be released. Part of our job is to make sure they can properly function in the wild, which means being able to hunt and catch their own food. It's the only accurate way to know with certainty that a bird has recovered enough, especially after an injury - more specifically, an eye injury. It's easy enough for a bird to catch onto the routine of us presenting them food that doesn't run away, but they need to demonstrate to us that they can fend for themselves. It's life and death for them out there. If they can't function, they don't leave.
Live-prey testing is where I draw the line. I find it totally impossible to throw a live animal, cousins to many we have raised, in with another to be eaten. We tried it once and once only. Spouse went to the pet store and bought a small white mouse for a screech owl hit by a car. Spouse put the mouse in with the owl on a freezing cold night. Around midnight, he went back to check and found the mouse uneaten and curled into an unresponsive ball. At that point, spouse lost heart and brought it in. We revived it and wound up with a pet mouse I named Lilly.
So now we outsource. We send all our raptors to a raptor rehabber nearby who is more hardened to the realities and willing to do the dirty deed for us. Thank goodness.