MarkECIN,
Here is a link to a solar motion light. I installed one for almost the same reason and it works great for now. I have alot of gray foxes visiting my daughters two ducks and installed this on a tree and it chases them away for now.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93661


Dreaming of the pond!