Winter finches are coming, and here's what to feed them.

Word comes from Canada of movement south. A birder in Toronto, who gathers information about the tree seed crops to our north, is making that prediction. Seed crops from Ontario east are poor, he says.

The bird species that rely on them could be at your feeder, looking for a handout in a month or two. Visitors will be siskins, redpolls and purple finches, maybe red-breasted nuthatches.

The goldfinches, house finches, white-breasted nuthatches, doves, and cardinals that regularly visit your feeders will be there as usual. They don't migrate.

Which seeds are preferred by which birds?

There is a scientific answer, a confirmation, perhaps, of what you already know. Biologists at Millikin University in Illinois enlisted volunteers for a seed preference study a few years ago.

Over 20,000 45-minute observation periods were recorded in 38 states and three Canadian provinces. One-hundred and six species were seen by 173 birders. It added up to almost 1.3 million feeder visits.

Results of the study — which sound definitive — were published by the Wildlife Society.

Chickadees, nuthatches and house finches were most abundant at feeders offering black-oil sunflower seeds. So were cardinals.

Red-winged blackbirds, given a choice, took white proso millet offered on platform or in hopper feeders. Not a mix, just the millet.

Redpolls, siskins and goldfinches favored sunflower chips and Nyjer (thistle) seed.

Sparrows, feeding on the ground, preferred the millet, a seed you would scatter. Think of sparrows, juncos, blackbirds, and doves.

The study showed that black oil sunflower, sunflower chips and white millet are the most common of the 10 seed types found in mixes.

Of course, you need not use a mix. We don't. We're exclusive with black oilers and thistle, one or the other eaten by our winter feeder visitors, even woodpeckers.

When shopping, read the contents information on the seed bag, or ask a clerk. You'll be looking for the same things the birds are seeking — high fat and protein content.

Not all seeds are created equal.

Black oil seeds have high nutritional content, as much as 55 percent oil and 20 percent protein in a kernel. Fat is an important part of winter bird diets.

The larger sunflower seeds, those with stripes, have a relatively hard shell. They can be difficult for a small bird to open. Black oilers have thinner shells, easier to hack or peel.

You can buy black oilers in the shell, shelled with the kernel intact, or the kernel in bits and pieces. Smaller bird species — smaller bites.

I bought a 50-pound bag of oilers in the shell in early October for $18.95. I shopped at a nearby feed store.

Birds know what they want. Less expensive bagged mixes, what you often see in supermarkets or big-box stores, usually contain seed types that birds will pick out and throw away. Bird food is an investment. Invest wisely.

Where your feeders are located can make a difference. Birds are more vulnerable to predation while they are eating. Feeders that are closer to cover — trees, bushes — are better.

Chickadees visiting our feeders almost always carry seeds to a nearby tree to open the kernel. It takes them several seconds to chop out the nut, time when they are not as alert to threats.

How the feeders look is not important. Ours are old, and look it. The birds care about function. Just keep your feeders clean.

We use plastic tube feeders. They can be hung high, to thwart squirrels and raccoons. Hopper feeders work well. Platform feeders are fine as long as you faithfully replace wet seed (or brush the snow off).

Bird appétit.

Read Jim Williams' birding blog at startribune.com/wingnut.