By Tom Horton|
The equinox officially ending winter is weeks away but from a great, densely-forested bend of the Potomac less than 30 miles down river from the nation's capital, come unmistakable notes of spring's first symphony: a rasping, clacking mélange of fricatives and gutturals; din of a ravening, demented mob; howls, screams, moans, croaks, a growling and whooping, a gargling with oyster shells; utterances learned, perhaps, from pterodactyls, belonging to a time not of this earth's.
Anyone not clued as to the source would be tempted to flee the woods, groundhog-like, back to the car, back to another month of winter. But press on for deep in the woods lies a prime example of what James Kushlan, director of the nearby Patuxent National Wildlife Research Center, calls "one of the great spectacles in nature."
It is a heronry, in this case one of the Atlantic coast's largest colonies of great blue herons. Some 2,000 have assembled near the little southern Maryland town of Nanjemoy to mate and nest and rear their young, gorging on spring and summer's protein bounty from the fecund shallows and marshes of the Chesapeake Bay region.
It is February, in the glow of predawn, when the herons return to begin anew the cycle of their year, says Calvert Posey, an amateur naturalist and lifelong resident of the area. Four times in the last half century, Posey was actually standing beneath the nest trees at the very moment the great blues arrived from wintering grounds as far south as Central America and Cuba. Each time a lone bird would glide in on wings that extend six to seven feet and circle the nesting grove, shattering the still with a series of terrible croaks. The scout would flap off as silently as it came. Then within 20 minutes, wave after wave of herons, in flocks of 25 to 50, would appear, flailing down onto the hundreds of crude, stick-built nests that crown the uppermost branches of the highest oaks and pines.
Footprints of the Great Blue Heron
In the days and weeks that followed, Posey would sometimes watch for hours as the birds began a combination of mating ritual and nest building and repair. For such reasons and the fact that their arrival was invariably around Valentines Day, Posey has always referred to the herons as "the love birds."
Not one of our 50 states claims the great blue heron as its official bird - but most could, without apology. Regally-plumed, strikingly colored and standing four feet high, it is among the most noticeable and ubiquitous of North American wading birds.
Everyone who lives near a merge of land and water, from ocean beaches to Grand Canyon gorges, from tidal marsh to farm pond, roadside drainage ditch to trout stream, has seen great blues standing sentinel there, sinuous neck and marlinspike beak cocked for a lightning lunge at passing prey. Indeed, up every major continental river system to the capillary ends of its drainage, no bird has achieved a more intimate and arresting fit within the North American landscape.
The great blue heron and its extended family, the Ardeidae (herons, egrets and bitterns), represent an extraordinary degree of evolutionary fitness. Fossil records indicate ardeids have been around for at least 14 million years, and a species virtually unchanged from the great blues we see today was stalking prehistoric swamps 1.8 million years ago.
Even within a family noted for adaptability, the great blue is remarkable. Consider its diet for example. Bird books generally list what a species eats - but with great blues it might be easier to list what they won't eat. Though they feed heavily on fish and crustaceans, when the need arises the great blue shows formidable skills as an upland - and even urban - hunter; and the size of its prey, usually swallowed whole, would impress anything short of an anaconda.
So it is that hungry great blues have been observed conking on the head and swallowing sora rails and adult muskrats around Chesapeake Bay; also stalking and eating gophers on public soccer fields near San Francisco Bay. A great blue was photographed on a parking lot in New York City, a large, limp Norway rat seized in its bill. And then there was the heron on Smith Island, a crabbing community in the middle of Chesapeake Bay, that made it through a winter freeze by dueling successfully with a mother cat for members of her late-season litter.
Such a supreme opportunist, the great blue heron would seem to have few problems coping with the 21st century. Indeed, its numbers appear to be stable or increasing across most states based on 30 years of random volunteer surveys. This may be due in part to the subsidence of DDT in the environment. The pesticide, banned about the same time calculations of heron trends began in the 1960s, accumulated in aquatic life and in the birds that ate it. A result was thinner eggshells and lower hatching success. Even today breakdown products of DDT remain and studies of great blue heron eggs show shell thickness has not quite returned to that of pre-DDT samples preserved in collections.
Another likely key to the great blue heron's success has, ironically, also sentenced thousands of them to death annually, the result of how we humans create landscapes that inadvertently turn out to favor highly-adaptive species of wildlife.
Exploding populations of white-tailed deer are an example. The sprawl of suburbs into the countryside has made a deer-friendly quilt of lawns, gardens, shrubbery, woodlots and farm fields; a de facto refugeÑplenty of food and cover yet densely populated enough to discourage deer hunting. Similarly, great blue herons have been as quick as any bird to capitalize on the upsurge in recent decades of backyard ornamental fish ponds, "pay to fish" recreational lakes, and storm water detention basins, as well as fish hatcheries and fish farming ventures. It has been like an open invitation to a banquet and aquaculture companies have responded by obtaining federal damage control permits to shoot as many as 2,500 great blues a year (otherwise they are protected by an international migratory bird treaty and other laws dating from the early 1900s).
Another bird success story - the comeback of bald eagles - may increasingly collide with great blues who fear few other creatures but have been known to summarily abandon a whole nest site when a pair of eagles decided to nest there. Eagles prey on heron chicks and sometimes even take adults. They also frighten herons off their nests with deadly results. Within moments the crows that cohabit many heron colonies swoop in, winging away with the herons' unguarded eggs speared on their beaks.
Eagles are coming back strongly enough to have been removed from their endangered classification nationwide in the U.S. and a majority of Americans now live in the coastal regions most favored by nesting great blues. Indeed, many wildlife experts think that if the highly-adaptable great blue has an Achilles heel it is probably the shrinking number of places suitable for its nesting colonies.
It is a paradox that while most people have seen great blue herons foraging singly for food, very few have been privy to the spectacular, cacophonous group settings of their breeding colonies or witnessed the complex repertoire of courtship and bonding rituals on display there. That is partly because great blues prefer to nest in the highest trees available, frequently 100 to 150 feet above the ground and obscured by foliage; also because they seek, wherever possible, solitudinous sites, isolated from intrusion by humans and mammalian predators.
The great blues' predilection for isolation in their nesting appears to be their primary defense against intruders. For all their hunting prowess, size, and formidable bill, the herons offer not the slightest defense of eggs or young, flapping off out of sight with scarcely a protest when intruders approach.
The herons' need for such places amid an increasingly settled landscape can produce some odd and unexpected juxtapositions. For example, Bloodsworth Island, an uninhabited 5,000-acre marsh in the middle of Chesapeake Bay, seems perhaps the unlikliest place of all. Home each spring and summer to hundreds of great blues, Bloodsworth is also an active U.S. Navy bombing range. Over the decades it has been strafed and bombarded by all manner of jet fighters and shelled by destroyers anchored off its shores.
So far the herons haven't seemed to mind. The colony there even appears to be growing, possibly with evacuees from a large heronry on Smith Island, some 10 miles to the south, where a pair of nesting eagles set up shop a few years ago.
While naval warfare exercises on Bloodsworth have always been restricted to outside the herons' main colony, charred stumps of trees confirm that mistakes did happen. So it is that the island's great blues now nest mostly on a small forest of artificial platforms, layered atop one another, jutting from six-by-six, salt-treated timbers erected by the Navy. The result is a unique opportunity to observe great blue herons en masse, unusually close to the ground and unobscured by so much as a limb or a leaf.
At times I have observed heron couples in the throes of springtime amore, touching gently, almost sensuously-thigh to thigh, breast to breast, bills tip to tip; and in this posture it happens that their glossy necks, curving fluidly between chest and beak, form something akin to the shape of a valentine. Watching them gazing steadfastly into one another's lidless, unblinking eyes, it is not hard to recall old Calvert Posey's moniker, "lovebirds," and to believe that something more than just instinct is at work.
Facilitating selection of a mate by great blue herons may be the best explanation of why they gather in colonies to nest. Only in dense groups can herons go through the considerable annual "comparison shopping" exhibited by both males and females before forming pairs in a reasonably short time. This in turn allows them to get on quickly with the all important business of reproducing.
Great blues lay from a couple to half a dozen eggs, greenish-blue and roughly the size of a hen's. By April or May, after a month's incubation time, virtually every nest has its complement of fuzzy chicks, all bills and legs. As many as four hatchlings may make it to fledging, though often one or two of these get evicted from the nest by its larger brothers and sisters. Once on the ground a chick is doomed. Adults seem oblivious to the plight of young thus disenfranchised.
As June and full summer rolls torporously over the marshes, the chicks are almost as large as adults though still weeks away from being able to fly. They often set up a fierce clamor before the human eye can detect an approaching adult. Alighting on the edge of the nest, the adult submits to having its bill grabbed by the young, which triggers a regurgitation of half-digested food into waiting gullets.
Feeding now becomes the adults' full bore occupation. A heron family at this point requires a daily caloric intake equivalent to the needs of a grown human. The parents may range out a dozen miles or more from the colony to forage. Their bright courtship colors fade, and their amorous displays all but cease as raising a family becomes serious business; it is hard not to think of parallels to the human condition.
By August, the spectacle that began in February amid sleet storms and frigid nor'easters, that continued through spring thunderstorms that blasted the herons and their chicks with 50 mph gusts, is winding down. The young, most flighted, are scattering from the colonies to begin fishing and foraging on their own. They are fully as large and developed as their parents now but perilously far from being as capable of feeding themselves.
It is estimated only one in five juvenile great blues will survive to breed in their third spring; the biggest reason for such high mortality appears to be the considerable difficulty they experience in learning to catch the large fish. They are among the least kinetic of the herons in feeding, wading very slowly or, more often, waiting motionless for hours before striking with such enthusiasm their whole head, neck and chest enter the water.
Watching an adult great blue tweezer-like grasp fish of up to a pound or more in their bills (they do not spear prey), one can appreciate the difficulty. They often stab at their catch for several minutes to subdue it; then they must position it so it will slide down their throat (the wrong way with stiff-spined fish can mean a slow, painful death to the heron). The relative few who do master the requisite techniques can look forward to a long life, 20 years or more, as even bald eagles prey infrequently on full-grown blue herons.
Compared with the glorious and haunting bugles, trumpeting and honking of other long-necked birds - the cranes, the swans, the geese - the great blue may at first seem to have been sorely shortchanged. Fishermen around Chesapeake Bay used to say the heron sounded like it had just gulped what it thought was a juicy soft crab, cursing: "CHRRRIIIST! I swallowed a hard one!"
But you cannot observe them for long before realizing they are in fact a bird that is eloquent beyond words. Herons, all angles and curves, have a body language without peer. Their collapsible, extensible frames can shift from shrunken to regal in a trice. They write their own ancient language, posing with gangly delicacy, stark as runes, against a rising moon or setting sun. Fishing motionless and upright, where the tip of a marshy point slips beneath the water, or flapping low across a river toward the horizon, great wings reflecting on the surface, they frame the merge of sky and water in a perfect parenthetical expression.
There is virtually no broad, formal protection for heron nesting sites, and logging and development seem certain to foreclose more and more options for nesting herons as the coastal regions continue to be desirable for both humans and birds. But there is some evidence that the ever-adaptable great blues can adjust to the human presence, even during nesting. In coastal areas like Chesapeake Bay where channel dredging generates mountains of spoil there is a growing trend toward creating islands, or restoring eroding ones, with herons as potential beneficiaries.
It seems a good bet that if we humans do our part to preserve wetlands for feeding and untrammeled open spaces for nesting, the marvelously adaptable great blue heron will meet us at least halfway.
This article was edited from Great Blues Are Going Great Guns, which originally appeared in the April 1999 edition of Smithsonian. Reprinted with permission from, and much gratitude to, the author and Smithsonian magazine.
Tom Horton is a noted author, naturalist and outdoors enthusiast who has written five books about the Chesapeake Bay: Bay Country, Turning the Tide, Swanfall, Island Out of Time, A Memoir of Smith Island in the Chesapeake Bay, and Water's Way. His weekly column appears in The Baltimore Sun.