Most bird species need water, not only to drink but to bathe in. If you provide flowing water you have the best avian magnet you can find because most birds can not resist the attraction of moving water. One of the most important aspects of attracting birds to your yard is to provide fresh water. Birds will flock to a waterfall or stream or even a fountain much more readily than they will a still pond or bird bath.
My wife and I built a pond and waterfall (what is known these days as a water feature) seven years ago and we love it. Our pond is about 12 feet in diameter and holds about 1000 gallons. In our pond we have several Shubunkin gold fish, many, many frogs and a multitude of water plants. As soon as we built the pond, I mean within days, we had frogs and birds and all kinds of creatures visiting us. The pond produced water skimmers, water bugs and literally hundreds of damselflies and dragonflies, as well as all the frogs, in very little time.
There is one thing that I feel is important to mention here. Maintaining a healthy pond is fairly labor intensive. This is especially true if you have fish in your pond. You must check your nitrite and ammonia levels,check your water hardness (KH - a pH stabilizer), keep your pH balanced and maintain proper salt levels. The whole idea of a fish pond is to create a natural environment for the fish. Goldfish and Koi like their water to be slightly alkaline. A pH level of 7.5 is perfect for them, 7.0 being neutral. To keep the pond slightly alkaline, the water hardness should be above 100 ppm to help stabilize the pH level.
With a good biological filter, the nitrite and ammonia levels in an established pond should always be at 0 ppm. Electrolytes are absorbed from the water by the fish's gills and are essential for the uptake of oxygen and release of carbon dioxide and ammonium across the gill membrane. Keeping a salt level of 0.1% in a pond with plants will maintain the proper electrolyte level in the pond water for Goldfish and Koi.
The oxygen level in your water is another important attribute of water quality. If you have a waterfall feeding your pond this should not be a problem. Keeping a pond in a natural state of balance is not as hard as it sounds if you have water plants and fish. If you have a biological filter and a waterfall, and you check your water weekly (and don't over feed your fish), you will be fine.
There is an alternative however if you want to have all the benefits of the soothing sound of the water and the visual waterfall, without all the maintenance. It is called a pondless or vanishing waterfall. This is how it works.
Instead of a pond at the bottom of the waterfall, the water cascades down a short stream and dumps into a pondless basin where the water pump lives. It pumps the water though a hose back up to the top of your waterfall where the process starts all over again. The pump chamber and pump are covered with rock and the flowing water disappears into the rock-filled basin.
With a flowing water system like this, filling up the basin to compensate for evaporation is all the maintenance you have to do! These pondless waterfalls come in kits that you can install yourself starting at around $500. There are also self-contained, artificial rock fountains made of fiberglass and resin if you don't want to do any digging.
If you are not interested in a water feature in your yard, the next best thing is a solar powered water fountain. These water fountains are the latest technology in birdbaths and fountains. They are powered entirely by the sun, they have a hidden reservoir so you don't have to fill them up everyday and they are made to keep a constant water level in the bowl. Another alternative is a simple container fountain with a decorative pump that will produce the flowing water that is so attractive to birds.
Whatever you decide is the best solution for you, a clean water supply is essential to attracting birds, even if it is just a shallow ceramic bowl. Just remember the water must be kept clean and if the bowl is more than a couple of inches deep you need to put some rocks in the bottom for the smaller birds to climb on to keep them from drowning.
If you don't have some kind of water source within your backyard habitat yet, consider all of your options and get some fresh, flowing water out there! You will be amazed at the amount of wildlife in your neighborhood that will come to visit, no matter where you live.
Happy Birding!
