Q: How often, really, do I need to clean my bird feeders?

A: I'm glad you asked that question, because this is a topic that simply doesn't get enough attention. We aren't doing birds any favors if we offer them food in filthy feeders — these spread diseases that can sicken and even kill avian visitors.

Some of us may assume that winter's cold is enough to kill off harmful bacteria, but this isn't always true. The two major bacterial diseases that can be transmitted from bird to bird at feeders are salmonella and avian conjunctivitis, both of which can lead to bird deaths. The Wildlife Rehabilitation Center in Roseville sees a peak in both diseases in January and February, proof that cold doesn't necessarily prevent these illnesses.

In winter, birds bunch up at feeders and, if healthy, their bodies can generally fight off salmonella infections. But birds in less than peak condition due to lack of food or water or injury might succumb.

Dr. Leslie Reed, a wildlife veterinarian at the rehab center, notes that salmonella can be spread when bird feces come in contact with their food. And conjunctivitis passes between birds as they rub against feeder surfaces.

So hygienic feeders are very important. I'd recommend cleaning feeders at least twice a year, at the end of summer and again at winter's end. Four times a year is even better. Start by tossing any old seed, and then use the standard "recipe": Clean feeders thoroughly, then rinse in a solution of nine parts water to one part chlorine bleach (this kills bacteria). Rinse feeders thoroughly again, dry them, then fill with fresh seed and replace them outdoors. If you use inexpensive plastic tube feeders and find them hard to clean, toss them out each year and buy new ones.

Linnea Carlson, who owns Chickadee's House Wild Bird Store in Roseville, says "Clean feeders can be the difference between life or death to our feathered friends." She gives these tips to customers:

• Have many bird feeders, since more feeders mean less crowding and less sharing of diseases.

• Clean feeders at least four times a year.

• If seed gets wet, toss it out, clean the feeder and refill with fresh seed.

• If you see sick birds, take down and clean feeders or replace them with new feeders. Wait two weeks to hang clean/new feeders.

To be on the safe side, wear gloves when you're washing out feeders, but you needn't worry about catching either of these diseases yourself.

Bad shells?

Q: After I sweep up under my feeders, should I put the sunflower shells in the compost heap? Is there a danger of spreading disease?

A: Excellent questions: It's great that you're cleaning up under feeders, because this area can be a source of contagion for ground-feeding birds. The heat in the compost pile should kill off the pathogens, but black oil sunflower shells carry a mild toxin that suppresses plant growth. For this reason, I've always tossed such shells in the trash, but I read recently that the toxin breaks down among composted materials, although this takes a long time. Some gardeners spread the old hulls in areas where they want to kill weeds.

Sparrow factory

Q: I'm going to get rid of an old purple martin apartment, since it's used only by sparrows. Can you suggest another bird we might try to attract with a house and is there a good book or other resource on this?

A: It's good that you're eliminating a sparrow factory. How about setting up a nest box for a chickadee or house wren, both of which commonly nest in back yards? Choose a box that has a small entrance hole, to keep out bigger birds (1 ⅛-inch diameter for chickadees, 1-inch for wrens). And the best book on the subject of nest boxes and birds that use them is Carrol Henderson's "Woodworking for Wildlife," third edition. Even if you don't plan to build a nest box, the book is crammed with useful information.

Long-billed woodpecker

Q: A woodpecker with an unusually long beak has been visiting our suet feeder. What are its chances?

A: Thanks for sending the photos of this odd woodpecker whose beak is so long it resembles a hummingbird. There are reports of this kind of deformity around the country, especially among chickadees in Alaska, although the cause is not yet known. This bird is lucky it can visit your suet because it surely can't forage normally. I hope you can continue to provide suet cakes throughout the seasons, and maybe even smear some peanut butter on tree bark, since the bird is going to need some help to survive. Here are two links with information about this condition:

http://alaska.usgs.gov/science/biology/landbirds/beak_deformity

http://dotearth.blogs.nytimes.com/2010/11/09/bird-sleuths-stymied-by-beak-deformities

Habitat for hummers

Q: What's the best spot for my hummingbird feeder?

A: You'll have the most success in attracting hummingbirds if you place your feeder in its own microhabitat. Hummingbirds spend much of the day perching, so put the feeder near a small tree or arbor or some other perching spot. They also like to feel safe from predators, so they'll appreciate some shrubs or evergreens for hiding. And they seem to have an affinity for water, even though they don't bathe the way songbirds do, so having a birdbath nearby is a good idea. If you have more than one hummingbird around, it's a good idea to provide several nectar feeders, with some distance between them, so one bird doesn't corral all the feeders.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at val​writes@comcast.net.