There are a few international members whom do as rats are harder to find. There is a little nutritional differences the big one looks to be lower calcium but that could be supplemented. Avians are a common prey item for sub adults in areas (according to predator/prey studies in the northern part of the range) So there can be no question they can and do eat birds in the wild. The real question is why bother? I assume you have a reason, just keep in mind there could be down sides some royals are hard to switch from one prey item to another, having a bird eating Royal that is 3400gm and eating small quail might pose a problem down the road.