By Scott Shalaway
TO MIGRATE or not to migrate, that is the question.
For some birds the answer is simple. Loons, grebes, nighthawks, swifts, hummingbirds, flycatchers, swallows, warblers, vireos and tanagers–all predators of live prey–migrate. Downy Woodpeckers, chickadees, titmice and cardinals–birds that can survive on seeds and berries in winter–do not.
But some birds seem confused by the question. Robins, bluebirds, towhees and Great Blue Herons are among this group.
Some robins and bluebirds migrate, but for the past 20 years I’ve always found these two thrushes wintering in my woods. Towhees usually depart my feeders by Christmas and return in early March, but this year they’ve lingered and have weathered several mornings of sub-zero temperatures.
Great Blue Herons, those tall gray waders that patrol streams and lakeshores, are a puzzle. They are abundant along the Florida and Gulf coasts in winter, and yet there are always a few that winter as far north as Ohio, Pennsylvania and West Virginia. As long as open water remains, their favorite food–fish–is abundant.
But now streams and even rivers are frozen, and yet a few great blues remain. The smart ones head south, even this late in the season. The hardy few that stay behind move from streams to fields and eat small mammals, especially meadow voles.
If the extreme winter weather we’ve experienced the past week persists, I suspect even stubborn great blues will head south. And in March they will return.
Found along virtually every waterway in North America, great blues often escape detection despite their size. Usually they stand quietly in the shallows scanning the water for fish. When a fish swims within reach, the long powerful neck explodes to full extension.
Great blues grab small fish crosswise in their bill then lift their heads and finesse the fish until it can be swallowed headfirst. Larger fish, likewise, are swallowed headfirst, but are caught by spearing with the long pointed bill.
Despite its impressive size, a Great Blue Heron can be difficult to spot. It can stand motionless for long periods of time, so our eyes often miss it. Only when we glimpse a sudden movement along a shoreline do we notice its presence.
More often we see a great blue flying overhead. The seven-foot wingspan, slow wing beats, neck drawn back in an “S” curve and long legs trailing behind the body make Great Blue Herons easy to recognize. The blue-gray body and black and white neck and head are usually lost in silhouette.
Many people see these tall, long-legged birds and call them cranes or storks. But cranes and storks rarely visit here. Where cranes and storks live, however, there’s an easy way to tell them apart. Cranes and storks fly with their necks extended. Herons, and egrets, for that matter, fly with their necks pulled back in an “S’ shaped position.
Just a few minutes spent watching a heron hunt teaches any patient observer that many strikes are unsuccessful. Like any other frustrated fisherman, a great blue will eventually walk or glide to another spot. Despite the great blue’s attraction to water, its diet is not limited to fish. It also eats frogs, snakes, crayfish, insects and even mice, shrews and small rats. The varied diet may make feeding young herons a bit more manageable, especially in dry years.
Unlike many birds, Great Blue Herons are communal nesters. These rookeries, as nesting colonies are called, contain scores to hundreds of nests. Both parents take turns incubating four or five eggs for about 28 days in late spring. Newly hatched young remain in the nest for two to three months before fledging.
An active rookery can get crowded and noisy. A single large sycamore may hold a dozen or more nests. Fortunately, rookeries are usually in remote woodlands where detection and disturbance by humans is unlikely. –Pittsburgh Post Gazette