Bird of Myth and Elegance
With neck-twisting mating rituals and 28 behaviors just for foraging, herons have long beguiled poets and scientists alike
Picture this. The moon has set early over the marsh, and clouds have veiled the constellations. In the pitch blackness, a great blue heron stands still, as herons have stood for millenia. Fish dart in the inky shallows, sensed but not seen. And so the heron nibbles with its bill at a patch of feathers on its breast, then sprinkles powder onto the water. In a flash, a phosphorescent glow lights the scene, exposing a school of shiners. With a lightning thrust, the heron seizes two minnows in its twin-pronged spear.
Beleve it or not? Not! Yet bygone stories of herons using a luminous powder on nocturnal fishing trips persisted well into this century. No wonder; Deliciously fantastic beliefs have followed the long-necked and long-legged birds through the centuries and across oceans. And even as scientific scrutiny has debunked the myths, the truth about these elegant creatures has proved no less beguiling than the fiction-inspiring as much poetry as research.
Standing 4 feet tall, with a wingspread of 6 feet, a familiar sight in any wet place, the "hernshaw" of England and the "blue crane" that colonists found wading about the marshes of New England commands attention. A trio of herons surprised by philosopher and naturalist Henry David Thoreau in the last century "seemed to oppress the earth, and hush the hillside to silence, as they winged their way over it."
Nine other herons and egrets (herons adorned with showy nuptial plumes) nest in North America, often in spectacular mixed colonies along the Atlantic and Gulf coasts. But the great blue heron is the one all of us on this continent are most likely to know, for it ranges almost anywhere from the Mexican border to Hudson Bay and the Alaska Peninsula. Bird-watching legend Roger Tory Peterson once watched one of the huge birds cruise down Manhattan's Fifth Avenue at a leisurely 20 miles per hour, two wingbeats a second, "its rubbery neck in a loop and its collapsible legs trailing like loose baggage."
Those long legs are a fragile assembly of thin bones and light tendons. Unlike some water birds that land with a splash, if not a crash, a heron must alight with care to avoid crippling its appendages. According to the lore of country folk, herons either built their nests with two holes in the bottom to allow a sitting bird to dangle its legs in comfort, or the birds straddled their nests, legs splayed over the edge. The truth, of course, is that a heron simply folds its legs and gently settles on its clutch.
In treeless habitats, great blue herons readily nest on the ground or in tangled shrubbery, atop a pile of marsh grasses, in the prickly arms of a cactus or on cliffs. But in a classic swamp-forest rookery, which can vary in size from a few pairs of herons to several hundred, the birds set up housekeeping in the highest limbs of the tallest trees. One great sycamore near San Francisco, 120 feet tall, once held 41 great blue nests in its upper stories, plus 28 nests of black-crowned night herons.
A newly built heron nest is nothing more than a few dozen twigs arranged in the crotch of a tree, a platform about 18 inches wide and so flimsy one can count the eggs from the ground. Over the years, as the birds add sticks that become glued together with gallons of guano, the nest grows into a massive structure solid enough to hold a man. In 1921, one 250-foot spruce in a Vancouver park held 37 nests; the enormous conifer stood mantled in gray and naked of needles, having succumbed to the flow of effluvium from adults and nestlings.
"Their profuse ordure [and] the decaying fish which fall from the nests make a heronry far from pleasant," remarked birdman-businessman Arthur Cleveland Bent in his monumental Life Histories of North American Marsh Birds. More than whitewash and half-digested carp rain from above. If gawky nestlings, clambering over the branches of their nursery, make a misstep and tumble down to the ground, parents ignore them-but not predators. A pack of wolves recently was observed regularly visiting a heronry in northern Wisconsin, feasting on lost chicks and dropped fish.
Alligators congregate near rookeries in the Deep South, gobbling not only doomed young, but raccoons intent on nest raids. The relationship is so mutually beneficial that when a commercial farm in Florida moved its 'gators to a new pond, the great blue herons that nested overhead moved with them. One huge wading bird colony at the mouth of the Suwannee River is notorious for its teeming and fat cottonmouths!
Fishermen of yore were convinced that a heron's foot exuded oil that enticed fish within range of the bird's five-and-ahalf-inch serrated beak. A formula from the year 1740 for a witches' brew, Unguentum Piscatorum Mirable, to be smeared on fishing lines included heron's fat as well as cat's fat and "Man's fat [which] you may get of any surgeons who are concerned in anatomy." To debunk this myth for his 1954 book on the grey heron (spelled "gray" in this country), the Old World counterpart of our great blue heron, British naturalist Frank A. Lowe dropped heron's-foot extract in an aquarium. The fish ignored it.
Nor do herons wiggle their toes to imitate worms, although the snowy egret stirs its bright-yellow foot in murky water to attract fish. Indeed, all herons have repertoires of feeding techniques, and they are capable of inventing new ones on the spot. Able to choose the right method for particular places and prey, herons and egrets living in a crowded rookery are able to divvy up food resources to the benefit of all.
Scientists have named 28 common foraging behaviors, from "wade or walk slowly," used by all herons, to "under-wing," in which a tricolored heron or a snowy or reddish egret twists its head beneath an upraised wing in order to fish in the shade.
For the great blue heron, patience and immobility are its stock in trade. Body erect, head and neck outstretched, it will "stand and wait" until a fish swims within striking distance. One observer on the California shore reported to Bent that a heron would "stand by the hour on a sinking raft of kelp fronds, though it leaves him submerged to the belly."
As for a great blue heron's food preferences, just about anything that swims, scuttles, slithers, runs, flutters or flies-and might conceivably be swallowed-is on the list. In the Far West, great blues even eschew fishing to stalk pocket gophers and grasshoppers in arid fields. On occasion, a heron's gluttony proves fatal. Great blues have choked trying to swallow 2-foot
long lampreys or died when the spines of a big catfish or bullhead pierced the neck, lodging the fish in the throat. Audubon Society scientist Sand Sprunt once unwound a large water snake from the neck of a heron that had seized it by the head. "It was a question," he said, "of who would kill whom."
The great blue heron's only serious enemy, however, is the eagle. Bald eagles have been known to develop an appetite for breast of heron, attacking adults and raiding nests. Scientists studying herons on Puget Sound suspected eagle forays for the failure of one small colony to produce a single fledgling in 1988.
If the great blue is our largest and most voracious heron, the prize for understated elegance could arguably go to the tricolored heron. Writing early in this century, when joie de vivre was an essential component of ornithological literature, Bent recalled his first encounter with the bird then known as the Louisiana heron: "What beautiful, dainty creatures they were, their slender forms clothed in bluish gray, blended drabs, purples, and white, with their little white plumes as a nuptial head dress. How agile and graceful they were as they darted about in pursuit of their prey."
Lacking the wispy, flowing aigrettes coveted by milliners, the tricolored heron escaped the shotgun slaughter that ravaged populations of white-plumaged herons a century ago. By default it became the most abundant heron in Florida's mangrove jungles, across Louisiana's tidal marshes and on Texas islands where thorny chaparral is segregated into crammed subdivisions for tricolored herons, reddish egrets, snowy egrets, great egrets and great blue herons. But though the tricolored's ornamentation in breeding season is less than spectacular to the human eye, ephemeral color changes in its soft (unfeathered) parts guarantee to capture the attention of a mate. In the passion of spring, the tricolored heron's legs turn maroon, the bill turns turquoise, eyes turn scarlet.
As courtship gets underway, an early-arriving male will claim a territory as large as 30 feet in diameter. At first he will drive away all intruders of either sex with intimidating threat displays or aerial pursuit. But soon females begin to wander through the territory unchallenged, appraising the male's posturing from a distance. And as more males settle in to stake claims, the defended territory shrinks and shrinks until it includes no more than the single bush holding the nest.
Whenever possible, the tricolored heron builds its nest in the shade, for dark coloration is a serious disadvantage in sun-baked rookeries. The feather reflectance of a snowy egret is 80 percent; a tricolored heron's is only 13 percent. Naturalist Helen Cruickshank once watched a tricolored heron, incubating its eggs on an exposed nest and suffering from heat stress, repeatedly dart to a shallow pond and splash water on its back. Tricolored herons breed through Central America to the shores of Ecuador and Brazil, and scientists are still looking for an evolutionary explanation for the presence of such a dark bird in such hot climates.
Scientists also have tried, with some success, to interpret the elaborate nest-side displays of mating herons. But riddles remain. Sir Julian Huxley, the renowned British biologist who studied life in a Louisiana heronry in the 1920s, was perplexed by the sudden excitement that would grip a pair of tricolored herons sitting side by side like a happy couple on a park bench.
Huxley wrote: "Upon some unascertainable cause the two birds raise their necks and wings and, with loud cries, intertwine their necks [which] are so flexible that they can and do make a complete single turn round each other-a real true-lovers'-knot. This once accomplished, each bird then-most wonderful of all-runs its beak quickly and amorously through the just raised aigrettes of the other, again and again, nibbling and clappering them from base to tip." He added, "Of this I can only say that it seemed to bring such a pitch of emotion that I could have wished to be a Heron that I might experience it."
One does not have to be a heron, however, to know the real story behind the mythical glow-in-the-dark feather dust. Powder-producing feathers do in fact exist-in three paired patches on a heron's breast, rump and flanks. And if the function of these unique "powder downs" is not magical, it is no less marvelous. For the feathers continually grow from the base as they disintegrate at the tips into a substance that the birds use to clean their plumage.
Preying on fish, eels, frogs, salamanders and such-then regurgitating the catch to hungry and clumsy offspring-is a messy business that leaves a heron's finery fouled with oil and slime. So the bird gathers the powder in its bill and then methodically pulls its wing and body feathers through one by one. After the dressing absorbs the grime, the heron scratches away the residue with the claw on its middle toe. Once again the heron is suitably dressed for its role as a graceful and elegant addition to our watery landscapes.
Not far from his home in New York's Hudson River Valley, writer Les Line can visit great blue herons nesting in the median strip of the Taconic Parkway. Tennessee-based photographer John Netherton will publish a book of images of wading birds in 1994.