Great blue herons are such a familiar sight in summer that a lake, pond or waterway seems bereft without its own long-legged stalker along the shore.

North America's largest heron stands about 4 feet tall, and its 6-foot wingspan can suggest an eagle in flight. But wait — this bird has long legs trailing behind it, and a long neck tucked into an "S" shape as it swoops down to land on the edge of the water, not eagle characteristics.

They're migratory birds, and the first great blues returned to our area right on schedule this year, with several sightings reported on St. Patrick's Day. These early birds were ready to take a chance on finding open water along shoreline edges for stalking fish.

The rest of the birds followed in fits and starts. By early April, a group of six great blues was spotted huddled in adjacent trees at the Bass Ponds in the Minnesota Valley National Wildlife Refuge in Bloomington. The birds' body language, with backs to the wind and heads tucked, spoke volumes about our wintry spring weather.

We think of these big wading birds as laid-back and languid, because they're most often observed standing motionless along a shoreline. Or we see them meticulously stalking prey, lifting one long leg after the other in slow, deliberate steps.

But this approach is the genius of the heron family — they're extremely patient birds, often waiting for prey to come to them. (Think of the black-crowned night-heron, not moving a muscle for hours as it perches on a branch over the water.) Masters of stillness, herons often engage in long periods of inactivity, burning few calories as they stand and wait. And this lack of motion often helps confuse prey: When a great blue roots itself to a spot in the water, small fish may mistake its two long legs for reeds, failing to recognize the danger they pose.

They're highly successful predators, switching from stillness to lethal hunting mode in the flash of an eye, with a lightning-fast strike of that long neck and sharp beak when prey comes into range.

It's startling to think of great blue herons as carnivores, but of course they are, with a diet dominated by fish and frogs and the occasional small mammal. These herons also consume crayfish, small turtles, salamanders, snakes, dragonflies, grasshoppers and even smaller birds. Everything goes down the bird's gullet whole before passing to the stomach, where strong acids break down all but the most indigestible bits, even fish bones.

Noisy nesters

Although they hunt alone, herons gather together when it's nesting time, in groups called colonies or rookeries, often made up of dozens of pairs. They build their nests high in trees, usually in a stand of deciduous trees. The birds are commuters, flapping daily between their rookeries and favorite fishing spots. Rookeries are noisy (and smelly) places, full of the guttural grunts of adults and hissy calls of hungry young birds.

As adept as they are at capturing prey, some great blue herons have learned to let humans do their work for them. In Florida and Gulf Coast states, as well as around popular fishing lakes in our area, great blues sometimes patiently stand near a fisherperson casting into the water, waiting for discards.

For such large birds, these herons are easy to overlook. But if you adjust to their slowed-down pace, you'll observe a hardworking bird, a master at its craft.

More about herons

Nest cam

Get a bird's-eye view inside an active great blue heron nest on Chesapeake Bay along Maryland's eastern shore:

Watch out

The Wildlife Rehabilitation Center of Minnesota treats a few great blue herons each year, some suffering a broken leg, lead poisoning or because they're young, emaciated birds not yet able to keep themselves adequately fed. "They are one of our more high-stress and dangerous patients," says Dr. Leslie Reed, senior veterinarian and director of veterinary education, "and we always wear protective eyewear" [to prevent a stab in the eye].

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