Disregarding the intentional bird feeding people do, several species have figured out that some human activities create dining opportunities far from our backyards. For instance, some have developed the habit of patrolling parking lots, where cars may come off the road with fresh "bug-kill" stuck to their radiators. Rather than having to chase down the live bugs themselves, the birds in such places just have to beat the competition to the juicy dragonfly, bumblebee or mayfly that had the bad luck to be over the road when the car or truck zoomed by.

I recently saw a wholly unexpected example of such adaptability. While waiting in my car for a green light at an intersection, the movement of two birds in rapid flight caught my eye. A larger bird was chasing a smaller one. As they neared another car that was waiting for the light to change, the smaller bird dove at the car, and ducked into its front wheel well.

Its pursuer veered away at the last second, and apparently did not see the small bird exit from under the other side of the car, because it gave up the chase. It was then that I realized by its proportions that it was a small hawk, very likely a sharp-shinned hawk, or perhaps a kestrel. I've seen sharp-shinned hawks take songbirds in my yard, and they have a pretty high success rate when they fix on a target.The small finch or sparrow that used the idling car as its escape route was fortunate indeed.

This weekend was not only a time when much of northern Minnesota experienced a reality check with a dumping of new snow, but a time of continued northward migration for many birds that have wintered to the south of us. Although I see and hear many Canada geese where I live, it's less common to hear the flute-like calling, and see the graceful, measured wing beats of whistling swans in formation overhead. This weekend was one of those rarer times.

My first encounters with swans came while duck hunting. They are typically seen high overhead, but occasionally a group may swing by low enough to give you a real sense of how much larger, and how different in proportion they are, from geese. Unfortunately, some waterfowl hunters have mistaken swans for geese, much to their chagrin, and perhaps also their financial loss in fines for killing a protected species.

Whistling swans and their larger trumpeter swan relatives differ physiologically in ways other than size. One difference might be best appreciated by a band instructor. The windpipe of both species of swans passes through their breastbone. In the trumpeter swan, the windpipe has a very prominent curve that is absent in the whistler, which not only adds length to the airway, but certainly changes its resonance and the sound it produces.

Swans, like other waterfowl, typically migrate in V formation. This has nothing to do with dominance, but is an evolutionary adaptation to the challenge of migrating long distances. It's been estimated that flying in V formation can reduce the effort needed by as much as 40 percent. This is due to the beating wings creating an "air vortex" that allows trailing birds to pass more easily through the air. Lead birds do not benefit from such air vortices, and when one tires it falls back in the formation, to be replaced by another. What an enviable example of "fuel economy."

There were other migratory bird sightings over the weekend. On a still-frozen pond, a pair of great blue herons walked awkwardly on long, spindly legs, looking much less graceful than they usually do when they're seen wading in shallow water, looking for a fish or frog for their next meal.

It's uncommon to see herons walking entirely out of water, though you'll see them posted at the end of a dock, sometimes even atop a boat lift. Most often, they're seen wading or flying. As soon as there's open water at the edges of ponds or lakes, they'll be there. Even sooner, they're found in the shallower, slacker areas of rivers and streams, which are ice-free before still waters.

Of course, other wild fowl are moving northward up the rivers, and gathered on small ponds that are partly free of ice. More bufflehead and goldeneye ducks have arrived, and now also ringbills and bluebills; just the thing to gladden the hearts of duck hunters who have missed them greatly since the close of last autumn's hunting season.