ALWAYS IN SEASON: Migrating birds come in many sizes

From the bird world this week comes news of big birds, little birds and birds that are somewhere in between.

The big bird is the American bald eagle.

One of these magnificent creatures lifted out of the cottonwood tree near our house west of Gilby, N.D., on Thursday morning. We had a couple of inches of snow overnight Wednesday -- more than in Grand Forks. My guess is that the eagle was passing by and our big, old cottonwood tree -- a relic of the homesteading era, I imagine -- was an appealing shelter.

Of course, eagles are not so unusual in our area as they once were. Several pair nest within an hour or so of Grand Forks, in the riverside forest along the Red and its tributaries.

It's now possible to see an eagle almost any day during nesting season.

But eagle numbers definitely rise during migration, as more northern birds move south. Eagles go as far as they need to find food.

The critical issue is food supply.

For wintering eagles, this usually means open water where they can catch fish. Important regional wintering sites are below Garrison Dam in central North Dakota and Below Randall Dam in southeastern South Dakota. Both are on the Missouri River.

Although they take fish, eagles are not especially efficient hunters, and they seldom pursue prey on land. Instead, they eat carrion.

In years of late snowfall, eagles can be common in northeastern North Dakota feasting on gut piles left behind by hunters.

Nearly every year, large numbers of eagles sometimes spend early winter around Devils Lake, where they sometimes take waterfowl caught in the ice.

Like other raptors, bald eagles take advantage of weather conditions for migration. A warm fall day with rising thermals can mean large numbers of eagles on the move. Good places to see them are along the main stem of the Red River itself, which seems to serve as a kind of highway, complete with big trees for rest stops.

The ridges that line the valley to both the east and the west can also be good. That's likely what brought the eagle to my place overnight Wednesday. The house lies between two of the beach ridges that border the valley. Air rises from the valley along these ridges, easing the eagles' flight.

Eagles are not the only big birds that take advantage of this geography. Earlier in the week, when it was already cold but not yet snowing, several flocks of Tundra swans passed.

The little bird of the week is the golden-crowned kinglet, one of two species of these tiny birds that occur here, most abundantly in the fall. Both are very small, grayish birds. Ruby-crowned kinglets have rings around their eyes, conveying a bug-eyed look. And they have reddish spots on their heads. But these are hard to see. Golden-crowned kinglets are a little more cooperative in this regard. Their head spots are easier to make out. Their faces seem striped; there's a white line above the eye and a black line through it.

The kinglets are truly tiny birds. The ruby-crowned version is two inches shorter than a House sparrow and the golden-crowned is smaller yet.

Look for kinglets in fairly heavy cover, often foraging at or just above the ground or in the outer tips of branches higher up. Here, the kinglets search for insects, which make up most of their diet.

Kinglets have a wingspan of about seven inches, and bald eagles seven feet, so there's lots of room for in-between birds.

Among these were the first rough-legged hawks of the season, which appeared in open grasslands last week. These raptors have come down from the North. They'll hang around into early winter, perhaps longer if there's little snow and hunting remains good.

So far, I haven't seen snowy owls, which like much the same habitat as rough-legged hawks. These birds can be common in our area, beginning in early November.

The peak of migration for another in-between bird probably occurred last week, too. American robins were abundant just about everywhere, it seemed. At my place, they gorged themselves on buffalo berries and crabapples.

But on Thursday, after the snow, they were gone.

Jacobs is editor and publisher of the Herald. His column about birds and the natural world appears Sundays.