An extremely dry Florida spring has put the largest nesting colony of wood storks in the United States in jeopardy. At the National Audubon society's 11,000-acre Corkscrew Swamp Sanctuary in the Big Cypress area of southwest Florida, some 750 nesting baby storks apparently are losing a fight for survival.
The colony is one of 19 in Florida of these white storks with black heads and black wingtips.
The birds nest high in 100-foot-tall cypress trees. Most of the trees this June are crowned with 11 to 15 rickety stick nests. Each nest originally held two fuzzy, white stork chicks. But many now are empty.
Parent storks, with wingspreads to 5 1/2 feet, glide into the nests in a regular flight pattern, bringing food for their young. But instead of finding fish near at hand, the adult storks have to travel miles. Some of the birds, identifiable because they have been tagged, have been known to fly 70 miles away to Lake Okeechobee in search of food. even that big lake, however, has been depleted by the dry weather.
Having to forage so far afield, the parent storks can provide only once-a-day feedings for their young. That is not enough to sustain the fast-growing baby storks, which have been succumbing at an increasing rate.
Storks need about two months of dry weather to bring the young to the fledging (flying) stage. Normally, Corkscrew Swamp averages 13 inches of water and provides sufficient fish, snake, and baby alligator for food. But this year it is dry.
If the young storks have not fledged by the start of the summer rainy season -- also the hurricane season -- survival is unlikely. This year, for the second year in a row, the storks nested late -- in april. The almost-daily tropical rains started on June 1.
"The little ones didn't quite make it this year," said Alexander Sprunt, research director for the National Audubon Society at Tavernier, Fla. "The wood stork is confused, and I won't be surprised if the baby wood storks at Corkscrew Swamp fail to fledge this year."
Mr. Sprunt says the south Florida wood stork population has problems with the changes in the ecology. A major contributor to the change is drainage of the swamps, either directly or as a side effect, for such projects as farming, building highways, and home building.
Corkscrew Swamp Sanctuary is located in Collier County, where an active conservation group is keenly aware of the problem. Weirs and dams have been built by the county canals and lakes and to attempt to compensate for the swamp drainage.
The wood stork is on the endangered species list for the state of Florida but not on the federal list.
Evidence that entire colonies of wood storks (Mycteria americana) are in serious difficulty showed up in 1974. Not one of a group of newly hatched birds tagged at Lane River Rookery in Everglades National Park was ever reported after fledging.
Sprunt says that the statistical curve of the wood stork population in Florida does not go sharply downward, but fluctuates -- with an overall downward trend.
"You could fledge almost all the storks from a colony," says-Sprunt, "but, if the birds have severe stress from lack of food before fledging, they may be in such poor condition that they may be unable to live. The whole production for a year may not make it."
Audubon Society records indicate that the stork population in Florida has been falling about 4 percent a year.
In the early 1930s there were 75,000 of the storks in Florida. Audubon Society statistics place about 12,000 wood storks in the entire state this year.
Breeding pairs numbered 4,600 in the state's 19 wood stork colonies in April, 1980. This group fledged 1.3 young per pair, "about what they have to produce to maintain a stable population," according to Sprunt.
The probable loss of the entire 1981 production of wood storks at Corkscrew Swamp is not considered a turning point in the survival pattern of the stork by some biologists. If environmental conditions improve, there could be three good production years ahead, says Jerry Cutlip, manager-biologist of Corkscrew Swamp Sanctuary.
Mr. Cutlip "will not make any dire predictions" about how many baby storks will be lost at the sanctuary. But he is not optimistic.
He adds, however, that man can help solve the problem: "Man can stop draining the swamps."