
ewww. Nope - none of the above.
It was to stop
this behavior from a very bad cat:
That's Bex, btw, the little angel in the top shot. It's hard to tell from this crappy cell phone shot, but she is dipping a paw into the water and flicking it into her mouth. She would park herself there and do it for several minutes, get bored, wander off, then return. My other cat, Finn, just liked to crouch low nearby and wait for a bird to not be paying attention and then attack.
The fence is wrought iron and I took a gamble it would be the perfect foil to the cats, while not bothering the birds at all. Works like a charm - the birds go for the water, sit leisurely on the edge and bathe/drink and are now totally safe. Neither cat has bothered to wriggle in there, like I was afraid they might. Brats.