public boolean actionMigrate(Fauna actor, Target point) {
    if (point instanceof Nest) {
      final Nest nest = (Nest) point ;
      if (Nest.crowdingFor(this) < 0.5f) return false ;
      if (Nest.crowdingFor(nest, species, world) > 0.5f) return false ;
      
      if (! nest.inWorld()) {
        nest.clearSurrounds() ;
        nest.enterWorld() ;
        nest.structure.setState(Structure.STATE_INTACT, 0.01f) ;
      }
      actor.mind.setHome(nest) ;
    }
    return true ;
  }