Geese 'whiffle' as they approach landing.

Q: When a flock of Canada geese flies in to our local lake, it looks like they start fighting as they drop toward the water. What's that all about?

A: A flock of Canada geese does look fairly disorganized as the birds come in to land but this isn't aggressive behavior. Instead, in order to land quickly without having to go on a long glide, the geese are rotating their bodies, twisting and turning to spill the air pressure under the wings that's kept them in the air. Some geese even do a full barrel roll to help slow themselves down and allow for a quick drop. These tactics are called whiffling, and if geese and mallards and other waterbirds didn't do this, they'd need to soar great lengths before they could slowly glide in.

More cardinals, please

Q: I love seeing cardinals against the snow. How can I attract more of them to my feeders?

A: Cardinals aren't hard to please. They're big fans of black oil sunflower seeds and safflower seeds, too. They have fairly big feet, so they don't like to have to grip a perch to dine, and most suet feeders don't suit their large beaks. Instead, they prefer to visit hopper, tray and domed-saucer type feeders, where they can stand easily. Add in some peanut bits and small balls of suet, and the neighborhood cardinals will drop in morning and evening. They also feed on the ground, either picking up dropped bits under feeders or seeking out millet scattered for sparrows. Cardinals relish having access to water year round, so a birdbath heater is a good idea in winter.

Where do birds sleep?

Q: Watching the late afternoon rush at my feeders, I'm wondering where the birds go to sleep away the winter nights — do they use their old nests?

A: The birds you see in your backyard are spending the night not far away. I've seen cardinals grab a last seed, then fly into a stand of evergreens about 50 feet away, where they'll perch on a sheltered branch for the night. House sparrows huddle up in a shrub or small tree, goldfinches perch near a tree trunk at night, and chickadees adopt a cavity — a hole in a tree, a break in a stone wall — for nightly naps. If birds build their nests in cavities (like chickadees, bluebirds, woodpeckers) then they'll sleep in cavities, too. But it's almost unheard of for birds to use last summer's nest as a night refuge.

Noisy robins, mystery food

Q: I saw a flock of robins in a deciduous tree in my neighborhood recently and they were making a lot of noise as they were busy eating something. Do you know what kind of tree it was and what they were eating?

A: The photo you sent shows a hackberry tree, one of my favorite native trees in forests, parks and backyards. The berries of hackberry trees ripen in the fall and are prized by many bird species, especially robins, providing meals at a time when most other food sources are disappearing. And birds are the prime way that this tree's seeds get dispersed, notes Welby R. Smith in his "Trees and Shrubs of Minnesota." The hackberry's warty, bumpy bark is very distinctive, and makes this tree easy to recognize, even in winter (see it here: https://extension.umn.edu/trees-and-shrubs/common-hackberry). Robins are big fans of fruit, too, especially in winter.

Toasty toes

Q: Two mourning doves showed up at our heated birdbath late in the day, and stayed there for quite a while, without drinking or bathing. Is it unusual to see them in winter?

A: Most mourning doves migrate away from the Twin Cities area in the fall, but some stay behind. I enjoyed your description, because they visit my heated birdbath late in the day, too. The doves don't seem to drink the water at this time, so I've suspected that they're enjoying the mild heat that the water gives off, before heading off to sleep away the winter night.

Behavior change

Q: We keep a bird feeder outside our third-floor condo window, and it's been very popular with goldfinches, sparrows and other birds. But the city recently cut down a dead tree across the street, where they used to perch. There's still a big cottonwood across from us, but the birds have ceased coming to our feeder. Thoughts, please.

A: You've observed in a very dramatic way how bird behavior may change with a change in their environment. Birds like to approach a feeder in stages, and almost always will perch in a tree or shrub before making that final leap to a feeder. They were used to perching in that dead tree and are still adjusting to its loss. The cottonwood may not be as comfortable for perching, with its high-up branches. I'm betting that they'll come to terms with this change and begin making visits to your feeders again.

Spotting eagles

Q: I want to see eagles this winter but don't want to take a long drive. Where might they be around here?

A: Minnesota has the largest population of bald eagles in the lower 48 states, so it's fairly easy to find some close to home. Since they're fish-eating birds, they favor open water, so look along the Mississippi River for these big raptors. Check where Minnehaha Creek meets the river in Minneapolis, or at Lilydale Regional Park and Hidden Falls Regional Park, both in St. Paul, and Kaposia Landing Park in South St. Paul. Glance skyward, too, because these big birds can often be spotted flying from one body of water to another. If you know the location of an eagle nest, this is a good time of year to spot eagles beginning to get ready for nesting season.

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 valwrites@comcast.net.