Say you're a bird and have had a tough day foraging for food and avoiding predators. Your living conditions are extremely primitive. Your bed is basically a branch on a tree and you never really have a chance to get off your feet. You're flying around and see a birdbath below an figure it would be nice to land, take a drink of water, then kick back and relax in a nice refreshing pool of water, maybe splash around a little.
Landings Can Be Hazardous
However, what have the humans put out in their backyard? It's a ceramic or glass birdbath. You come in for a landing and either skid over into the bushes below or splash headfirst into very cold water, even before you get a chance to get your feet wet. Ceramic and glass birdbaths are a hazard for birds -- there's no grip for landings! Many birds have had to suffer the embarrassment of other birds making fun of them after skidding off the slippery object. The mockingbirds can be especially cruel. Turkeys tend to make the most callow remarks, although they never really make use of birdbaths. Birds have a pretty good sense of humor, but they generally don't like taking pratfalls. If people think this sort of thing is funny, how about coming back home from your next winter vacation and to your dismay, the pilot discovers (a little too late) that your local national airport has not treated the glare ice on the runway? How that for funny?
Content Until the Bottom Falls Out
Another point about ceramic birdbaths, they crack and crumble if left out in the elements. The illustration below tells it all. The entire bottom cracked and crumbled. If a bird was taking relaxing and taking a bath in this hazard trap, the consequences could have been tragic. Again, if you think this is humourous, how would you like to be taking a bath and the entire bottom of you bathtub collapses to the floor below. I don't think you'd be happy about it, especially trying to explain to the paramedics why you got a tattoo in that particular place.
Little Feet Need the Grip
The solution is obvious. If you're going to place a birdbath in your backyard, use one made out of cement or stone. The birds and their little feet can grip and hold on to cement or stone. Stone can be expensive and difficult to find. Birdbaths in cast cement can be found in most garden supply stores or home stores. Unless you have a load of money, try to find a basic, low cost cement birdbath and stain or paint it yourself. Stain might be the best. You can even paint images, flowers or whatever if you want -- I prefer just a basic stain with a non-toxic acrylic spray coat. Here's what I tried after researching the internet.