You need both the counterweight and the spring as well as a narrow and distant treadle to defeat the rats. You also need to use the feeder as designed from day one, blocking a treadle feeder open for "training" just teaches the rats that the feed is there and makes them persistent. Crows and ravens are very intelligent and might learn to cooperate but that takes enough intelligence and discipline for three or four crows to stand on the treadle while the other crows eat and not rush forward to eat. And allowing birds access to a coop is a very bad idea for disease and pests, free range, yeah, no way out of that. But a feeder that is exposed to all sorts of critters is going to be much harder to vermin proof.
