Nature Notes: Great Blue Heron
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By Ed Robinson
You have probably seen this tall, graceful bird standing motionless along streams and ponds. As evening approaches, you will often see herons cruising with slow wing beats, their long necks folded in a graceful S curve, spindly legs trailing as they make their way to a quiet feeding ground. Waiting patiently or stalking with purpose along the shore, this sharp eyed predator with a lightning fast strike is the bane of shallow water creatures that catch his eye. The Harpswell Heritage Land Trust even chose to use a silhouette of this lovely bird for our logo.
I was thinking of these graceful birds yesterday as I observed one sitting in a large birch tree on our shoreline. The afternoon had turned quite windy and the heron found a comfortable perch for nearly three hours, probably waiting for the tide to go out. Great blues will use any wetland habitat including salt and freshwater marshes, lakes, ponds, and swamps. Sitting in my office, I often see as many as 12 great blue herons since they congregate in the eel grass beds at low tide. Opportunistic feeders, the birds prefer small fish but will take shrimp, crabs, aquatic insects, and amphibians. They have also been observed capturing small mammals, reptiles and small birds, almost always swallowed whole. Scientists have identified cases of herons choking on food when their eyes were bigger than their throats!
The great blue heron is found across most of North America, commonly ranging from Alaska to the Caribbean. On occasion, great blues have been found in Europe and even in the Galapagos Islands, a 500 mile flight from the coast of Ecuador! The birds we see in Harpswell in warmer months are capable of wintering here, but they generally follow our seasonal residents south to warmer climes for the winter, in some cases reaching South American countries. While generally considered solitary, they breed in colonies that can reach hundreds of birds called heronry.
Their nests are made from sticks and twigs, similar to those of the ospreys. Nests are normally in trees or strong bushes, but are sometimes found on islands or platforms that provide some protection from egg stealing creatures. Typically the female will lay three to seven pale blue eggs, and she is capable of laying a second clutch if the first eggs are lost. The birds are sensitive to human disturbance while nesting, and may abandon their nests if they become distressed. Both parents help in feeding their young, regurgitating partially digested food for the chicks. Once grown, great blue herons have few natural predators but have been observed being killed by eagles, great horned owls, large hawks, and in southern swamps, alligators.
The largest heron in North America, the great blue reaches over four feet tall, with a wing span that can exceed six feet. Thanks to hollow bones to facilitate flight, the mature bird weighs only five to eight pounds. At a distance they appear to be a lovely slate gray, but they have reddish brown thighs, light brown and black stripes on their flanks, with a black and white stripe on their neck. The head is paler in color, the face appearing almost white, but with a pair of black feathers showing from the eyes to the back of the head. The bill is generally a light yellow, but turns more orange for the breeding season.
The great blue heron will not win any singing contests, with a call that is best described as a rough croak, heard during breeding or when they are disturbed. But their beauty, their grace in flight and their determined manner of fishing, often in solitude, make them well worth your viewing time.