CHARLESTON, W.Va. -- For countless millennia, birds survived the rigors of winter without humans' help.Today, it's a little different. In backyards nearly everywhere, in summer as well as in winter, people put out food and watch the birds that come to eat it."Feeding is an age-old American pastime," said Rich Bailey, ornithologist for the state Division of Natural Resources. "Lots of folks put out food year-round, but most of the feeding takes place during the winter months, when birds need it most."Wild birds' natural foods become scarce during the winter. Plants no longer produce seeds, berries and fruit. Insects are far less active. In West Virginia, snow sometimes buries food that otherwise might have been available.Humans step into this breach by putting out all manner of stuff that birds like to eat -- seeds, suet, fruit, nuts, grains and even insects.Bailey believes people can enhance their bird-feeding experience by following a few simple guidelines:"When you think about setting up your yard to attract birds, think about what the birds are looking for," he said. "They want food, for sure, but they also need shelter."We have a species of hawk here in West Virginia called a Cooper's hawk. It likes to prey on birds that come to feeders. So it's a good idea to put your feeders near shrubs, bushes and trees that the birds can duck into when predators come around."Bird feeders -- especially those that hold seeds -- come in many shapes, sizes and configurations. Bailey sometimes gets asked which one is best.His answer: "It depends on what species of birds you want to attract. You want to bring in the widest variety of species while keeping away undesirable species such as house sparrows and European starlings." Bailey said a tube-style feeder would be a good one to start with."Tube feeders are long plastic tubes that usually have from three to six perches mounted outside of little feeding ports," he said. "The ports can be wide, or they can be very narrow. The ones with wide openings you'll want to fill with black oil sunflower seeds. Black oil seeds are smaller, easy for the birds to open, and they provide a lot of nutritional value."Black oil seeds bring in chickadees, nuthatches and tufted titmice. Those birds will always spill some seeds out onto the ground, and cardinals will come in to feed on those."Tube feeders with narrow openings are often called "finch feeders" or "thistle feeders." Bailey said they're designed to hold the tiny black seeds of the African yellow daisy, commonly sold as Nyjer, niger or thistle seeds.The term "thistle seed" is a misnomer. Some seed blends actually do include thistle seeds, and those should be avoided. Real thistle seeds lack nutritional value, and spilled seeds will often sprout into prickly thistle plants. The Wild Bird Feeding Industry trademarked the name Nyjer in 1998 to help consumers find the right product."Nyjer will bring in goldfinches, pine siskins and house finches," Bailey said. "The narrow slits on thistle feeders help keep house sparrows away. Their beaks are two wide to fit into the slits."Two other types of feeders can enhance the variety of birds that come to you backyard."I'd also recommend getting a suet feeder," Bailey said. "Suet is a combination of animal fat, fruit, nuts and even insects. People used to make suet cakes themselves, but now they're readily available commercially."Suet feeders are wire cages painted green that hold the cakes and give birds something to hang onto as they feed. This type of feeder brings in woodpeckers, wrens and creepers, plus a bunch of birds that hang out under the feeder to pick up crumbs."The final kind of feeder Bailey recommends is a platform feeder -- but only for areas free of house sparrows."It's basically a post with a wide platform on top," he said. "You can put sunflower seeds on it, cracked corn, peanut butter -- just about anything. Cardinals love platform feeders, as do evening grosbeaks and mourning doves."Many commercially available seed blends contain fillers such as oatmeal and millet. Bailey doesn't recommend them. "Millet really draws house sparrows," he said.One feature birds really like during winter is a heated bird bath. The heating element keeps the water ice-free, especially during cold snaps that freeze birds' other sources of drinking water."You might want to consider a bath that has a little drip attachment," Bailey said. "Birds love that drip feature."One often-overlooked aspect of bird feeding is keeping the feeders clean."We recommend cleaning them every two weeks with warm soapy water and a 10 percent bleach solution," Bailey said. "Keeping feeders clean helps prevent birds from getting salmonellosis or aspergillosis, which they can get from eating food from contaminated or moldy feeders."People who find dead or sick birds around their feeders should take their feeders down immediately and call the DNR's Elkins office at 304-637-0245. Bailey said bird enthusiasts should also call if they happen to see a hummingbird flitting around."Our ruby-throated hummingbirds have flown south, but sometimes rufous hummingbirds will fly due east instead of south and east, and they end up in West Virginia. For that reason, we at the DNR recommend keeping your hummingbird feeders filled until we get into the dead of winter. If a hummer turns up, it's unusual, and we would like to know about it."Reach John McCoy at firstname.lastname@example.org or 304-348-1231.