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Winter is the most challenging season of the year for Minnesota's birds. Food is scarce so they need to spend nearly every waking minute searching for enough calories to beat the cold.

The difference between birds' inner body temperature — around 105 degrees — and that of the outside air is much more pronounced in winter. Thus, their metabolism must be stoked continuously by feeding throughout the day, as if they were shoveling coal into a furnace.

This unrelenting need to consume calories is why many winter birds can be enticed to bird feeders. Out in nature, resources are spread around, so it's a bit "unnatural" for food to appear in one place. But once birds become familiar with a feeding station, they'll make it part of their routine.

Feeders almost never are the difference between life and death for our backyard birds but they do make their lives a bit easier, especially after a long night of fasting, or before heading off to their night roost.

And the reward for those of us who maintain bird feeders is watching the birds they draw in.

Chickadees dash in to grab a sunflower seed, then flit off to a branch to peck it open. Burbling goldfinches stack up at tube feeders filled with nyger and sunflower chips, while house finches seem to prefer safflower in a dome feeder. The minute I put out peanuts, the blue jays dart in to carry them away on trip after trip. They return so quickly I'm convinced they're stashing most of them around the neighborhood to eat later.

Juncos hop around under the feeders for seed bits scattered by the other birds. They're often joined by a flock of house sparrows that feed in a rush before scattering back to a large evergreen shrub where they noisily chatter.

The downy, hairy and red-bellied woodpeckers swoop in for shelled peanuts and suet bits. White-breasted nuthatches perch head down as they chip out chunks of peanut to eat or stash under garage shingles for later consumption.

Sometimes this dynamic changes quickly, with songbirds exploding into flight and disappearing. Or the backyard reveals no birds other than a woodpecker or two frozen in place on the peanut feeders.

What's going on? Almost invariably, a hawk has strafed the backyard, or is hiding in an evergreen.

Hawks are becoming a fairly regular feature around feeding stations, even in urban areas. Bird-eating hawks like Cooper's hawks have learned that small birds gather around bird feeders, and this makes their hunts much easier. A Cooper's hawk sweeps through my backyard several times a week, often perching on a metal arbor, its head swiveling as it tries to locate the now-hidden birds.

The woodpeckers freeze in place if caught in the open by a hawk, since their fairly slow, swooping flight makes them vulnerable to highly maneuverable raptors. (Red-tailed hawks sometimes drop by, as well, but seem more interested in the squirrel population.)

Once the hawk leaves, birds emerge from hiding to feed on the ground or at feeders, seeming to put the episode behind them.

The birds return many times a day, but as the shadows lengthen, they take one last seed and one last drink at the birdbath, then disappear for the night. All except the Northern cardinals, whose ability to see at low light levels allows them to stay out later (and show up earlier in the morning). Some winter evenings I may count up to 18 male and female cardinals shuttling from feeder to ground to birdbath, before finally disappearing as darkness falls. (As spring approaches, this behavior will end, as rising hormone levels make the red birds more territorial.)

One of the many lovely things about birds is that they make living look easy, but their lives are anything but. Having well-stocked feeders along their daily foraging routes gives them just a bit of an edge in a life-threatening season.

Hidden hordes

Some birds, such as blue jays, black-capped chickadees and white-breasted nuthatches, stashed food away last fall and these food caches can augment their daily hunt (if not locked away by deep snow). Squirrels or small rodents doubtless devour many of these small caches of food.

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