I think red tailed hawks and macaws could almost be the same size, if you google pics of people handling red tail hawks (falconry) and google people holding macaws you can see how similar they are in size.
Catalinadee one of our mods here has a hawk check out the pics of her flying it, it will give you the idea of size. CLICK HERE!
Now here's a macaw that just might be bigger then a red tailed hawk, check out these pics! CLICK HERE!
I'm going to go off the hyacinth macaw being the largest species and I'm going to go off weight. Lengthwise the macaw will always come out on top with their tails. Largest hyacinths anything up to 1700g. Largest female red tails 2000g. As their sizes can vary so much though they're almost the same really. Smaller species of macaw will be smaller than a red tail. Again, other factors would include sex etc.
I know Hyacinths are the longest in the parrot family, but I was confused about whether they were bigger or smaller than a Red Tail. I think I see red tails all the time when we're driving around, but I can't tell that much since we're moving. I've counted well over 70 of them.
Birds of prey are normally larger than parrots, but then macaws are pretty large. Eagles are definitely larger though.