I thought pidgeys were based of pigeon hawks or merlin as there known? I maybe wrong, plus it's not a rip off but there similar
As I said, it's more of a mash-up of birds. I don't really see any features from the Pidgey family that much resembles a Merlin specifically, so I think it's more likely to just be based on Birds of Prey in general.
Anyway, I think Birds of Prey have been overdone as the basis for the regional bird, so it perhaps they could base it on something like a Parrot or Stork. Although, I actually quite like all of the regional birds we've had so far, so I don't really mind what kind of bird we get next.