So I am having this kind of issue that when I install the mod other vanilla mobs won't spawn wherever I go they don't spawn that frequently. The mobs that I encountered having a issue to spawn are rabbits, pigs and chickens. Even ducks from environmental mod from Team Abnormals won't spawn. I am using the latest version of citadel and Alex's mobs. Cows, sheeps, horses, and bees are not affected.

You should probably crank up the Environmental duck spawn rate, and reduce the spawn rates of the AM mobs you're seeing the most of.