Water is simply the liquid of life. All living things require it, and all living things will remember where they can find it. Birds are no exception. They will visit water sources several times a day for the purpose of drinking and bathing. Water is vital to their survival and therefore a necessary part of any birder's garden. Whether a fountain, pond, mister, or any type of feature, it's a necessary part of a bird's day. In fact the more water features you add to your garden, the more likely you'll attract a wide range of birds, and they will discover the features you created for them.
Over the last couple decades, I've experimented with different types of water features to see what style is the most preferred with songbirds and hummingbirds. Simply put, the bigger the bird, the deeper the water, but every one of them prefers belly deep water or shallower. All birds that aren't your typical water bird have a great fear of water. Before they're comfortable with a water source they want to make sure they can feel the bottom with their feet. They're not like ducks, and they will not float. So when we create a feature for birds, we have to keep this in mind. The range of size in birds in my garden is typically from a hummingbird to a Northern Flicker, which means water depths should vary from 1/8 inch to 2 inches in many locations. Anything deeper and you won't get many birds attempting to bathe in it. Birds will typically touch down with their feet and then lower their bodies into the water, so a 2 inch maximum is more than enough for a bird the size of a Robin or Northern Flicker. For small songbirds, shallow water just over their feet is enough, but there are a few courageous birds that like to swan dive into some deeper water.
When I suggest a perfect backyard bird pond, I don't mean the most beautiful pond imaginable, I mean a pond logically designed for birds. I'll use my small fountain pond as an example. The depth ranges from 8 to 12 inches deep. It's not a deep pond by any means, but it's way too deep for birds to trust and use without some added features. So to attract the birds I had to think like them. I added special features to the pond so the birds would trust it.
1. First of all we added the fountain. Water gently flows over the moss and flat rocks which is a perfect location for small birds to perch, drink and bathe. It's not a fast flow to turn it into a bird water slide, but gentle enough to flow over their feet.
2. Secondly, I placed rocks close to the edge just beneath the surface of the water. If they can see objects just below the surface they'll test them out. Have different sizes of rocks, some breaking the surface and some slightly below. If the rocks are clustered they'll stand on the rocks breaking the surface and examine the others around it.
3. Thirdly, I laid some larger curved branches from one side of the pond to the other. The curve of the branch dips down into the water on one side, and then gradually backup out of the water on the other side. Birds will frequently land on the branches and slowly hop their way down to the depth they prefer.
4. Finally, create areas all around the pond where they can perch and observe all the structures you prepared for them. I left smaller branches attached to the larger ones in the water so birds can perch on them.
Birds love water, and I can tell you they will travel great distances just to get to your garden. Food can be found in many places, but water is harder to come by. I can promise you that if you create water features with many important structures built in, over time you will attract birds like you couldn't imagine. Know that birds are afraid of deep water, and keep that in mind when you create little features. Create many perches, rocks and plants all around and they will search them out and use them. Once they find their favorite perch, you'll start to recognize the same birds returning time after time, and day after day.