Thursday, November 18, 2010


Many people call the large, gray, long-necked and long-legged birds we see wading near shore “cranes.” But they are not. They are herons. The Great Blue Heron (Ardea herodias) is in the heron family (Ardeidae). It feeds by standing or slowly walking on its long legs, sighting prey, and then capturing it with a lightning-fast strike of the bill. The head is brought back and the prey swallowed, usually headfirst.

Prey that is not killed by the strike is manipulated in the bill for a time to dispatch it. Fish that have spines they can erect are thoroughly handled, so they are dead before they make the long journey down the esophagus. In some especially spiny prey species, the herons actually manage to break off the spines before they swallow the fish.

Although usually feeding in the water or at the waterside, the herons’ diet is not confined to fish. They feed on just about anything they can catch in the water, including frogs, salamanders, garter snakes, crayfish, and even large insects. They also spend much time foraging on land, especially in winter when surface fishes tend to go deeper. In the Pacific Northwest, voles are an important part of the diet, and it is commonplace to see the herons hunting in meadows and farmlands.

Foraging by herons is usually solitary, and they are quite territorial at that time, with long, sometimes noisy, chases when one gets too close to another. They also fly by themselves, but at high tides, sometimes several birds roost in the same tree or on the same sand bank, near one another. This heron is an adult, with characteristic black head plumes. Herons fly with their neck folded back. Their wings are very large, about the size of eagles that are many times their weight, and they allow the heron to fly very slowly and land in shallow water with scarcely a splash.

The other bird shown here is a true crane of the family Gruidae, quite unrelated to the herons. This Sandhill Crane (Grus canadensis) is only very rarely encountered near Puget Sound, although large numbers migrate through eastern Washington and many birds winter in the southwest corner of the state, especially in the Vancouver to Woodland area, where they can easily be seen in open fields and marshes.

Sandhill Cranes are gray, often tinged with brown, and have red naked skin on top of their head. Their long tertials (innermost flight feathers) hang over their rump and tail, giving them a quite different shape from that of a heron.

Cranes forage by walking slowly through their habitat, often a partially flooded meadow, with head forward. They watch for prey in front of them, which they grab suddenly and then swallow it. Although they eat some of the same things that herons do, for example small mammals, reptiles, and amphibians, they take very few fish and many more insects, as they forage mostly on land. Herons eat no plants, but plants feature prominently in the diet of cranes, especially grains, berries, and the tubers of aquatic plants. As they do for geese and ducks, federal and state wildlife agencies manage refuges for cranes by planting grains.

Unlike the herons, cranes are often seen in flocks, sometimes large ones. They spread out somewhat to feed but return to their flocks to roost and to fly about the countryside. In flight, their wing beats are rapid and their neck is held out straight. A distant flock might be mistaken for a flock of geese, flying in a line or vee formation.

Dennis Paulson

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