As you can see in the left of the picture, the water is almost to the rim of the stainless steel water bowl. The bowl is about 3 inches deep. (I still fill the water bowl for the birds or in case the neighbor's dog happens by. It has turned out to be a wonderful bath for the brown thrashers that nest in the forsythia each year.)
The gray treefrogs must love all this water. They set up a chorus around the back deck loud enough to raise the dead. If they get half a chance, they lay eggs in the rain barrel and buckets. If I don't get around to dumping the eggs before they hatch, I usually leave the tadpoles alone. Last night I was going to empty the rain barrel to get rid of the mosquito wigglers. I scooped off the frog eggs and then used the garden hose to siphon the water. Lo and behold, there was one full-sized tadpole. Maybe it had overwintered? Since I was draining out all his rain barrel water, I chased him with a pitcher, finally caught him, and transferred him to a bucket.
Even when I leave the tadpoles alone, I only see a few mature into frogs. Here is one little fellow I took a pic of last fall. You might notice he's no longer in length than the worms that fall off the sycamore tree and drown in the rain bucket.
Speaking of frogs, here is a link to a fun site which lets you listen to various frog sounds. I like the dreamy trill of the American toad. (I've heard about enough of those gray treefrogs for a while!) http://www.exploratorium.edu/frogs/tracker/
I'm not sure what that says about the excitement level of my life when the major event of a Friday evening is finding a tadpole in the rain barrel. But I sure rocked that tadpole's world!