Yes, because then (assuming the lid is air tight), you aren't limited to maintaining a water level in the rain barrel no hichger than the top of the waterer.
If it does not require the lid to work, then you should be able to fill it from the rain barrel via a siphon system. Now here's the trick. So the water will keep filling until the water in the rain barrel and the water in the water ER are at the same height. Meaning you will probably have to...
I am not familiar with that waterer design. It all comes down to the way it works. The waterers that are basically buckets upside down with a tray at the bottom of them only work under vacuum conditions. You can't use a supply from another bucket to keep them full. The waterers that work with...