What is living in your birdbath?

Birdbath sample and 100X field microscope

Since I had my microscope out to look at white fly nymphs I decided to take a look at what lives in the birdbath.  When there is no water in it many of the creatures encyst until it either rains or I fill it up with water.  During the summer you can see a reddish deposit on the bottom and I've read that this is carried in by the birds and is rotifers. A good place to see what grows either in your birdbath or garden pond is to visit Ron's Pond Scum.  An interesting web site that gives you lots of interesting photos of micro-critters and plants.  Sure would like to have his microscope and camera setup.

I was expecting to find rotifers but haven't seen a one so far.  It was pretty lifeless when I looked at it right after collecting the sample.  But I placed it in some sunlight and have spotted some nostoc growing.  Also there are a few critters swimming around in the soup but I can't I.D. them.  I've ordered a student microscope with zoom from 50-250X in hopes of getting a better look.  There is also a lot of dead plant tissue fragments in the mix that the birds brought in.

BTW I scrub the birdbath with a stiff brush and rinse out the debris each time I refill it with fresh water.