For the Louisiana climate, I have problems with fire ants, mosquitoes, and rats. I have a feed system very similar to the upright pvc with a small branch at the bottom to eat. In the evening I can screw on a cap to the bottom to cover the food and keep rats out. The branch is long enough to prevent scratching and throwing out feed. Ive tried several methods, including a trigger system where they peck the trig at the bottom of a bucket and feed falls into a pan below. That system was an ant and rat magnet.
Nice to know - but sorry to hear - about the rat magnet aspects of the trigger feeder - I am trying to transition to that right now as a way of providing feed that the wild birds can't get eat or poop in. The first girl learned it yesterday, so I was thrilled after several days of showing them and listening to complaints. My chickens did not take to a treadle feeder. I was hoping the trigger was something that rats wouldn't be able to figure out, or I could place it too high for them to get to, once the chickens are comfortable with the system...
I am also switching from pyrex bowls to a backyardflock.com cup feeder in a 2-gal food-grade bucket, once again to provide water that wild birds won't track around in. It's clear that, if left out and up, nighttime critters, either rats or skunks, are drinking from it, so I am starting to turn it upside down for night.