Pterodactyls? B-52 bombers? What are these looming, faintly ominous creatures in the sky?
They are great blue herons, largest and best known of America's herons, equally at home in Florida's freshwater swamps and along Southeast Alaska's rocky beaches.
Though nothing could be less graceful than a great blue heron coming in for a landing on a branch, they spend many hours roosting in trees, often in sociable groups. Our family has been privileged to have five to eight herons roosting in a stand of hemlocks and Sitka spruce along the shoreline in front of our house in Wrangell this past winter. Walking the dog in the early morning light or just before bed, we often startle the snoozing birds into raucous flight, but they return to their favorite branches when all is quiet again.
Contrary to their image as a solitary bird, great blue herons sometimes form large flocks on feeding grounds and often breed in colonies called rookeries or heronries. What a delight it was to see a band of nearly 20 great blues circling in the spring sky and over the water. Was it the sunny afternoon that stirred their blood? Great blue herons may also flock together for protection against predators, though they have few natural enemies.
Habitat destruction today is the most serious threat to their numbers.
Great blue herons usually nest in trees, near the top. Nests are made of intertwined branches and lined with softer material such as twigs, moss or evergreen needles. Southeast Alaska is the bird's northernmost nesting area and the birds can be seen in our region year-round. In the spring, males and females reach the nesting ground at about the same time. Males settle near last year's nests, then defend their territory, displaying and shrieking when females come near. New mates are chosen each year.
Three to five eggs are laid and hatch after about 28 days of incubating. Male and female take turns feeding the young, one always remaining at the nest. During the day the male watches the nest while the female hunts; at night the roles are reversed, according to the Canadian Wildlife Service. At eight weeks, the young fly from one nest to another, at times landing in the wrong nest. Then, they either stay in the nest, driving an occupant out, or are shooed away by the returning parent.
Picking their careful way around stones or standing motionless near the water's edge, great blue herons stalk their favorite food, fish. They hunt in shallow water, waiting for their prey to come within striking distance and moving only their head and eyes. When a fish comes close enough the heron folds its neck back, then moves one leg toward the prey. Unbending suddenly, the bird's bill darts into the water, catching the fish and swallowing it headfirst. A fish too large to be swallowed all at once will be dropped back into the water and grabbed again and again until it is quiet or sometimes taken to shore and devoured in pieces.
Though it prefers fish, a heron also will consume insects, crustaceans, amphibians and reptiles, mice and shrews, and aquatic plants. In flight, great blue herons are sometimes confused with sandhill cranes. Herons, however, fly with their long neck curved back into an S, while cranes fly with neck extended. And, despite their social inclinations, herons are often seen flying singly, while cranes generally travel in flocks.
Great blue herons stand 4 feet tall and have a wingspan of up to 7 feet. They really are more gray than blue with white feathers around the head, while black plumes adorn the back of their head.
This spring's cold but sun-filled afternoons lured our herons out to soak up the warmth on branches sheltered from the northerly winds. Now they have left for their private nesting grounds and only if we are fortunate will we glimpse a lone bird stalking dinner along the shore during the next months.
While frequently seen in Juneau, the birds are considered uncommon in Southeast Alaska - likely to be found here but not in abundance. Even a treeful, however, isn't enough to make this birder jaded. No matter what the season, I'll be pursuing this ungainly yet elegant bird with the same intensity as a great blue heron seeking its next meal.
Bonnie Demerjian watches great blue herons in her home town of Wrangell, where she is staff writer for the Wrangell Sentinel. The final Juneau Audubon Society spring migration bird walk meets at 7:30 a.m. Saturday, June 7, at Dredge Lakes. For details see www.juneau-audubon-society.org.
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