You could alter this setting
    # Prevent players from acquiring these mobs as a morph.
    # Leave blank to allow acquisition of all compatible mobs.
    # Formatting is as follows: <class>, <class>, <class>
    # Example: am2.entities.EntityBattleChicken, biomesoplenty.entities.EntityJungleSpider, thaumcraft.common.entities.monster.EntityWisp
    S:blacklistedMobs=
or
    # Disable the flight ability until a player has reached the nether?
    # 0 = No
    # 1 = Yes
    I:disableEarlyGameFlight=1