The bucket has a lid, with a 1/2" hole for the water to fall through. Adult chickens are tall enough to drink directly from the stream... you would need something tiny for a quail.
This is the exact one i built, except at the endpoint i let the water flow directly into the bucket instead of...
I have a little hydroponic garden... Basically a cheap $20 water pump pumps water into one end of the pipe, and it flows around and falls back into a lidded 5 gallon bucket with a small hole. My chickens love drinking water where the water falls back into the bucket