Great Blue Heron

Great Blue Heron Has Few Natural Enemies

“The Great Blue Heron,” said George Gladden in the 1936 edition of Birds of America, “is the largest of the truly American herons, and is known as a stately, dignified, and interesting bird by those who have observed it in other ways than over the sights of a shotgun or rifle.”  The long-necked, long-legged and elegant bird often fell to hunters who believed it “to be even more destructive to the spawn and young of game fish than to its other prey of frogs, crawfish, small snakes, salamanders and various water creatures which are more harmful than useful, not to mention grasshoppers and meadow mice.”  (The great blue heron is now protected under the Lacey Act and the United States Migratory Bird Treaty Act.)

In the estuarine waters of the Texas Gulf Coast, where my family and I lived for nearly two decades, the great blue herons stalked the estuarine shallows with a regal air and great patience.  They drove their rapier-like bills into the water to take prey with sudden and lethal swiftness.  They built colonies of several stick nests in the water oaks and other trees of the dense hardwood forests along the shorelines.  They complained loudly, in a hoarse kraak, kraak, kraak, if we disturbed them. 

In the deserts of the Southwest, where we have lived now for more than a quarter of a century, the great blue herons came as a surprise to us.  A major waterbird in the desert, hundreds of miles from either the Gulf or Pacific coasts?  Yet, here they are, stalking riverine environments, lakes and man-made ponds with a regal air and great patience. 

The Bird

According to the Audubon Society’s Master Guide to Birding, the great blue heron (called Ardea herodias by biological scientists) stands “about 4 feet tall with a wingspan of 7 feet…”  The largest of our herons, it weighs about 4.5 to 5.5 pounds.  (By comparison, our stockier bald eagle has a wingspan of about seven feet and weighs about 10 to 14 pounds.)

“The adult [great blue heron] has a white head with the sides of the crown and nape black, and short plumes projecting to the rear.  The neck is light gray, with a whitish ventral stripe; the bill is large and yellowish; the body is blue-gray, and the legs are dark.”  Sometimes, its belly tends toward white with dark stripes.  The iris of its eye has a distinctive yellowish gold color.  The juvenile great blue heron lacks the trailing plume on the back of its head. 

Like a crane, the great blue heron flies with slow swooping wing beats, its legs trailing, and it walks with long and deliberate strides.  Unlike a crane, which flies with its neck extended, the great blue heron flies with its neck folded into an “S” shape, its head almost resting on its shoulders.  In flight, the bird’s body seems disproportionately small compared to its wings.   “When the heron takes to flight, what a change in size and appearance!” said Henry David Thoreau (Thoreau on Birds).  “There go two great undulating wings pinned together, but the body and neck must have been left behind somewhere.”

If the great blue heron survives its first 12 months, when it is most vulnerable to predators, bad weather and food shortages, it may live 15 years.  With very good luck, it can live for more than 20 years.  The bird does seem to be accident prone, sometimes flying unwittingly, and fatally, into power lines or fences. 

Geographic Range and Habitat

The great blue heron, probably the best known of all the herons, covers a range that extends from southern Alaska and southern Canada southward across the entire contiguous United States and into Mexico, Central America, northern Colombia and Venezuela, the Caribbean Islands and even the Galápagos Islands.  Migratory populations breed in southern Canada and the upper Midwest, and they winter in Mexico, Central America and northern Colombia and Venezuela.  Year-round, or non-migratory, populations span most of the lower United States, from the Atlantic to the Pacific, including most of the desert Southwest. 

The birds claim fishing territories in the calm shallows of permanent water sources, including, in the Southwest, the Colorado River and the Rio Grande and their tributaries, the mountain springs and streams, the riverine marshes, and the impoundments.  Typically, they build nests in trees and shrubs near the waters edge, up to about 5000 in elevation, usually as part of a colony called a heronry or a rookerie. 

The Consummate Fisherman

While perfectly willing to raise a family in the company of others, the great blue heron prefers to pursue its passion, fishing, in solitude and with single-minded purpose.  It guards its fishing territory jealously.  Locating its prey by sight, the bird may fish through the night and the day, although it intensifies its hunt at dawn and sunset, typically the most promising time of day for all species of anglers. 

According to the Hinterland Who’s Who Internet site, the great blue heron, when fishing, may stand as if frozen in the water, furtively moving only its head and eyes.  “When a potential meal comes close enough, the heron slowly folds its neck back and moves one leg in the direction of the prey.  Suddenly, its entire body unbends, its head plunges into the water, it catches the prey in its bill, and it swallows it outside the water, using a deft movement of the head to drop the prey headfirst into its gullet.”  Alternatively, the bird may stalk prey, driving fish from hiding.  “…the great bird may be seen stalking slowly through shallow water, lifting each foot above the surface, and sliding it into the water again so gently as to cause hardly a ripple,” said Gladden, “and woe to the crawfish or salamander that does not observe that approach.”   In other instances, the bird may drop from a streamside perch or even from flight into the water to take its prey. 

Usually, the great blue heron takes small fish, which measure less than the length of its bill.  Occasionally, however, the bird gets greedy, taking a fish too large to swallow.  It may even choke to death on its prey. 

In addition to fish, the adaptable great blue heron often eats frogs, shellfish, insects, rodents and even small birds.  In some instances, it feeds nestlings a diet with a high percentage of rodents. 

Raising a Family

At about two years of age, the great blue heron – normally as reserved as the queen of England – discovers sex, and the male, especially, can become a perfect showoff.  Just as with the species we call Homo sapiens, “The male begins to display, attracting females, but repelling them,” said the Illinois Fish & Wildlife Internet site.

Come spring, the sexually mature male chooses a tree for a nesting spot, a site he will guard ferociously.  When females come near, “…males put on grand displays and shriek loudly…” said the From Hinterland Who’s Who.  Getting acquainted, the male and female crack their bills together tenderly.  They court with elaborate body movements around the potential nest, much like Homo sapiens court with strange-looking movements on a dance floor.  

If the feathered lovers bond, they promptly mate for the first time.  The male then begins gathering dead twigs, which his bride will use to build a nest several feet in diameter, sometimes lining the cavity with moss or pine needles.  “As a male heron with a twig returns to the nest,” said the Utah Division of Wildlife Resources, “Wildlife Notebook Series No. 14,” he is greeted by his mate with a ‘stretch’ display.  In this display a [female] heron stretches its neck outward and points its bill upwards in an arc while lowering its body by flexing its legs.  An ‘aarrooo’ vocalization accompanies the display.  …the feathers are fluffed and back and chest plumes are raised.”  The male raises its plumes and croaks softly (and romantically, at least, in the eyes of the great blue heron female).  He gives the female a twig as if it were a bouquet of roses.  The two clasp bills and move their heads back and forth, in a beakshake instead of a handshake.  They preen each other’s feathers lovingly. 

They mate sporadically, in very brief episodes, over the next several days.  Within a few weeks after their initial mating, the female lays a pale bluish-green egg, the first of four to seven she will produce during the next several days.  After the arrival of the first egg, the faithful parents take turns incubating the clutch, with each remaining on the nest for six or so hours at a stretch—a routine that will play out over some four weeks, until the first pale gray downy chick hatches.   

For the next several weeks, the parents must incubate the remaining eggs and, at the same time, brood and feed the demanding new arrivals.  When a parent returns from a foraging trip with food, the bird usually takes a perch a few feet away from the nest, perhaps steeling itself for the coming raucous feeding.  Meanwhile, the nestlings bob up and down, jostle and peck, squawking excitedly.  After several minutes, the parent flies to the nest and regurgitates food into the beaks of the rioting baby great blue herons or onto the floor of their nest.  The older and larger chicks bully the younger and smaller siblings in the scramble for food, sometimes pushing them from the nest to fall to their doom, according to the Hinterlands Who’s Who.  (Often only two or three of the sibling herons manage to survive.) 

Within a couple of weeks, a young heron begins to preen itself, stand upright and spread its wings.  A few more weeks, it ventures from the nest, a gangling adolescent, spreading and flapping its wings.  Soon, it makes exploratory flights to nearby trees or to the ground, always returning to the comforting refuge of the nest and parental feedings.  About two and a half months after hatching, the young great blue heron leaves its nest for good, setting out on life of its own.  If it survives the hazards of youth, when it is most likely to fall prey to crows, ravens, turkey vultures, red-tailed hawks, eagles, raccoons and human land development, it will take up the art and pleasure of solitary fishing and the annual rewards and trials of parenting.  Its parents, meanwhile, will dissolve their union when their last chick leaves the nest.  They will return the following year to pursue a new romance with a new mate. 

The Great Blue Heron’s Outlook, and Our Own

A large bird, the adult great blue heron has few natural enemies other than Homo sapiens, and its overall population remains relatively healthy in the desert Southwest.  However, the bird, which has a low tolerance for human encroachment, especially when nesting, may face an uncertain future in the wake of booming urban and suburban development.  It will serve as a measure of how well we manage and care for our water resources in the desert Southwest.  Thoreau held the great blue heron in such high regard that he felt it should be made a citizen of America.

By Jay W. Sharp

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