During the spring and summer months, it's easy to remember to fill feeders and water containers for backyard birds. But often, even those who conscientiously care for wild birds in warm months will forget that many of them remain in the area during winter and still need our help.

Birds' needs for drinking water, in fact, can become even more critical in the winter months when their natural water sources freeze. Although birds often use snow as a source of water, snow can glaze over with ice and become inaccessible as a water source, particularly in the coldest months. The most critical situations for birds are often when temperatures remain below freezing for prolonged periods, yet there is no snow to provide water.

If you do maintain a birdbath or other water source for birds, ensure that it is clear of debris and routinely checked for ice cover. Electric warmers are an ideal way to keep bath and small-pond water from freezing. They cost from about $15 to $30 for a small, non-thermostatic de-icer to about $40 to $70 for a high-watt, thermostatically controlled unit.

In the winter, a ground-level bath can be more effective than a conventional raised, pedestal-style bath since it has less area exposed for heat loss. Also, locate a bath or pond on the south side of a natural windbreak -- such as a house, fence or shrubbery -- to maximize the solar heat to the bath. Use a dark-colored bath or pond liner to maximize solar energy absorption.

When possible, use a bath or pond with moving water. This will attract both birds that come to feeders and birds that typically do not. If you've previously used only a still-water bath, you will likely have new birds visiting your yard. Some experts say that as many as 3 to 4 times as many birds can be attracted by simply providing moving water. Moving water gets the birds' attention, is healthier than stagnant water and helps alleviate the freezing problems encountered by unheated still-water baths and ponds.

A simpler approach to the moving water scenario is a dripper installed in the bath or pond. Usually, they are connected to an outdoor faucet and set at a regulated drip to keep the birdbath filled with fresh water. An added bonus is that the ripples created by the dripper help attract birds. When set at a drip rate of once per second, they use about one pint of water per hour. In areas where water conservation is critical, timers can be connected to automatically control flow. Standard drippers, which usually double as misters, cost about $40 to $60.

Commercially prepared seeds are fine for wild birds as long as they and the feeders do not get moldy. Studies have shown that black-oil sunflower seeds attract the greatest number of species. If you feed bread and other bakery products to your backyard birds, be aware that you might also be attracting nocturnal visitors such as raccoons. Suet is a good high-energy food that gives birds an additional boost to survive the cold.

Cat predation can be a major problem for wild birds that would otherwise come to a backyard feeder, bath or pond. For hanging feeders, make sure they are at least four feet off the ground. Cats and other bird predators hunt by surprise, so keep feeders and baths away from bushes and other predator hiding places.

Tom Gillespie works for the public affairs office of the N.C. Zoo.