Sept/Oct 2015For Wildlife Watchers: Wood Storkby Rob Simbeck, photo by Christy Hand
Sometimes, survival hinges on being out of fashion. In the late 19th century, herons, egrets and many other shorebirds were slaughtered by the thousands for their plumes, which were treasured by the makers and wearers of ladies hats. But consider the wood stork, lacking in distinctive breeding plumage and therefore relatively safe.
Unfortunately, habitat disruption eventually accomplished the fashion industry couldn't. Over the course of the 20th century, developers drained more than half the wetlands in the southwest Florida. Logging took out large swaths of cypress trees. Water levels were disrupted, and since the Everglades provided the wood stork with much of its U.S. nesting habitat, the effect was great. The number of nesting pairs in the U.S. plummeted from approximately 20,000 in the 1930s to fewer than 5,000 by the late 1970s. By 1984, they were listed as an endangered species.
Fortunately though, wood storks are resilient, and they have been moving northward, extending their breeding range as far as North Carolina. Their conservation status in the U.S. was upgraded in 2014 from endangered to "threatened." They have been particularly successful in South Carolina, where they were first documented nesting in 1981. In 2014, there were 2,501 wood stork nests in eight of our coastal counties. Productivity was also high, with an average of 2.2 chicks fledging per nets in the colonies that were intensively monitored.
Christy Hand, a wading bird biologist with the S.C. Department of Natural Resources' Wildlife and Freshwater Fisheries Division, sums up optimal conditions for wood storks this way:
"It comes down to food availability and water conditions. We had a wet year before and during the [2014] nesting season, which meant there was plenty of standing water prior to the nesting season [from February through July], which allows pre populations to grow. Between rain events, the pools of water shrink and concentrate prey."
Food sources in South Carolina are also more diverse than those in South Florida, says Hand, and our extensive network of managed tidal impoundments and tidal creeks provides foraging opportunities even during drier years. A wood stork feed by feel, immersing its large, slightly opened bill into shallow water and snapping it closed on small fish or other small aquatic creatures that bump against it. Feeding tactilely means it can feed successfully in muddy water or at night.
Wood Stork - Mycteria americana
Description: Three feet tall, five-foot wing span; for to seven pounds; featherless, leathery-appearing neck and head; white wings with black primary and secondary feathers.
Habitat and Range: Wooded wetlands. Nests in coastal South Carolina, but occasionally seen throughout the state.
Reproduction: Nests colonially in rookeries, ideally in trees or on islands surrounded by water deep enough to deter predators.
Viewing Tips: Do not disturb or approach birds too closely at any time. Good viewing areas include coastal wildlife management areas and national wildlife refuges.
"Many impounded wetlands managed for waterfowl are drawn down in late summer, coinciding with the period when fledglings depart from rookeries," says Hand. "This provides easy prey for young storks during the period when they are probably most vulnerable to starvation."
At the beginning of the reproductive cycle, a male wood stork stakes out a site in a tree, often one used by other wood storks as well as egrets, herons and ibises. There can be two dozen nests in a tree and hundreds in a rookery. He challenges other males with bill-clattering, neck stretching and grabbing. Males average seven pounds, about a pound more than females, and have a longer heavier bill, but they are other indistinguishable. An interested female will approach with her bill open and her wings spread until he accepts. As they bond, stork courtship behaviors include synchronized bill-clacking and preening, and they will stand shoulder-to-shoulder at the nest site. Those strong pair bonds are important, because both parents build and maintain the nest, defend it and care for their young.
"Storks will carry fresh sticks they have pulled from trees, many with leaves attached," says Hand. "They continue to add fresh sticks to their nest throughout the breeding season, even after chicks have hatched."
The female lays a white egg slightly larger than a chicken egg every day or so - three on average. Hatching is staggered, and the earlier chicks have the best chance of survival. Hatchlings weigh just two ounces and have short brown bills and cartoon-big-eyes. The adults share incubation duties, shading eggs and chicks from bright sun until, at four weeks, their feathers allow them to thermo-regulate. The young grow rapidly as the parents bring food from nearby or, if necessary, dozens of miles away.
"I frequently observe storks rapidly descending from high altitudes to their nests with their legs awkwardly extended forward and the air whooshing loudly as they use their wings to decelerate," says Hand. "They sometimes look as though they are out of control and are about to crash, but they always seem to land safely."
Tall and long-legged, the wood stork has a gnarled neck, a scaly dark brown head with a black patch, large black eyes, and a stout, downward-curving bill. In flight, it is a striking, almost majestic bird, riding thermals on five-foot white wings trimmed in black, its dark legs trailing a short black tail.
The young weigh twenty ounces at two weeks and three pounds at twenty-eight days. Parents alternate attending the nest and young while going off to feed, bringing back the prodigious amounts of food the nestlings require. Predators include crows, night herons and some other birds, as well as raccoons. Rainfall sufficient to keep enough water around the trees to allow alligators to deter raccoons is optimal. After the young fledge, at seven or eight weeks, they remain dependent on their parents for another two or three weeks.
During the post-fledging season (August to October), many storks that nest in other states visit South Carolina to forage. A small number stay through the winter, and some die of exposure.
"Even though South Carolina is an important nesting area," says Hand, "wood storks continue to require reliable winter habitat in Florida to be successful in the Southeast."
And it is habitat that continues to be of prime concern. Fortunately, says Hand, "Work is underway in the Everglades to restore habitat for storks and other species. Increased awareness of impoundment management practices that benefit waterfowl and also benefit 'value-added' species such as wading birds, shorebirds and seabirds might also be aiding in their recovery."
South Carolina is also actively managing its rookery habitat (see the feature story on page 28). There are several places along the coast where wildlife watchers can observe these birds from a distance, including DNR coastal wildlife management areas and national wildlife refuges. It's a great opportunity to see a success story that should leave us cautiously optimistic about what is still possible with man-made solutions for species facing man-made problems.
