My parental instincts, or just plain curiosity took over, so I removed the feeder so I could see down the top slot and see if there were still bees, or really so that I could see there were bees that were alive, having feared I had drowned them. And of course, they are fine. From the fuzzy picture, you can see they are certainly alive (yes, they all were moving, and were drinking the syrup. They jar was down about 1/3 of the way, which says to me it that it must be working. And certainly with 2/3 left in the jar after about 24hrs, I have not drowned them.
I also saw about 10 crawling around the entrance once I had removed the top. My guess is there are guard bees looking to see what all the fuss was about.