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The Brown Pelican's Return to Coastal Louisiana

Coastal Louisiana's brown pelicans have faced serious challenges across the past several decades, but they are now thriving where they once were extinct. This 2-part series explores their battle with pesticides, along with two CWPPRA projects that have been instrumental in the recovery and preservation of pelican habitat.

The Brown Pelican and Louisiana History

The brown pelican (Pelecanus occidentalis) has a storied connection to Louisiana. From Iberville's first coasting of the Gulf of Mexico's shores in search of the Mississippi's mouth in 1699, journals kept by those in his company recorded the populous colonies of the birds they encountered. After returning to France, Iberville would captain a ship christened The Pelican back to the New World in 1704, carrying with him some 24 "well-bred" girls to the burgeoning colony of Louisiana in hopes that they would provide an incentive for permanent settlements.

State of Louisiana Seal: "Union, Justice and Confidence"

It is said by some that William Claiborne, the territory's first governor after the Louisiana Purchase in 1803, was the first to suggest that the brown pelican appear on Louisiana's seal. No matter the rightful originator of the notion, a pelican feeding its young could be found on the seal as early as 1804. As for the bird itself, no less an authority than the painter and naturalist John James Audubon would describe the pelican as "one of the most interesting of our American birds", waxing rhapsodic as he went on to describe the species' feeding habits in his journal:

Look at them as they fly over the bay; listen to the sound of the splash they make as they drive their open bills, like a pock-net, into the sea, to scoop up their prey; mark how they follow that shoal of porpoises, and snatch up the frightened fishes that strive to escape from them. Down they go, again and again. What voracious creatures they are!

Lousianana state flag: "Union, Justice and Confidence"

In 1912, Louisiana adopted a state flag that featured Louisiana's state motto "Union, Justice and Confidence" and, once again, a pelican feeding hatchlings. And in 1966, the pelican received its ultimate due when it was officially named the State Bird of Louisiana. Yet in the very year it was adopted as the state bird, the brown pelican that had been recorded by Iberville's men and Audubon's brushstrokes had completely vanished from Louisiana's shores.

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The Brown Pelican's Disappearing Act

Arriving at the number of brown pelicans historically found in Louisiana is difficult due to the wide variance in reports across the early portion of the past century. In 1919, for instance, the state's population was estimated to be roughly 50,000 individuals. A 1938 survey, however, placed the estimated number of breeding pairs across the state at only 5,000. Later, in 1955, a survey estimated that 5,000 adults and fledglings could be found on East Timbalier Island alone.

However, in 1961, a scant six years later, no nesting pairs were spotted across the state's entire coast. And by 1963, only eight years after the East Timbalier survey, there were no brown pelican sightings whatsoever in Louisiana. The complete extirpation of brown pelicans from Louisiana's coast suddenly left the question of a baseline population a moot point. Clearly, the state's coast had served as home to a thriving, well-established population for centuries, but suddenly, inside the span of a single decade, the number had flatlined. To this day, the brown pelican's disappearance remains one of the most astonishing events in the annals of American ornithology.

It didn't take long for researchers to begin searching for causes behind the dieback and ways to bring the brown pelican population back to Louisiana. Immediately suspect as causes were a pair of tropical storms in 1956 and 1957 that had savaged the coastal barrier islands where brown pelicans bred and nested. Because over 90% of brown pelican nests are built on the ground, many scientists suspected that overwash across the islands had simply eradicated the nests across two successive years, dealing the colonies breeding setbacks from which they simply could not recover.

A flying pelican

Given that researchers had arrived after the fact and faced a paucity of forensic evidence, other theories vied for their attention as well. Some suspected that an unknown pathogen had swept through the colonies. Others suspected that human encroachment in the form of energy exploration and shipping activities had played a role. Still others suspected chemical pollutants ranging from pesticides to petroleum byproducts released from oil production facilities were to blame.

However, while the mid-60's found Louisiana's scientists investigating the phenomenon and putting the plans for a restocking effort in place, southern California began to experience its own brown pelican dieback, a decline that would leave only 10% of that region's population intact by decade's end. Fortunately for the scientists in California-and, ultimately, Louisiana-this time researchers were in place to observe the decline as it was happening. In short order, the scientists on the West Coast had solved the mystery. Thousands of pounds of the pesticide DDT (Dichlorodiphenyl Trichloroethane) had been discharged into Los Angeles County sewers by a single chemical plant. Upon entering coastal waters, the DDT had been absorbed by anchovies and other fish favored by the pelicans. The DDT molecule, while not water soluble, is fat soluble, and with a half-life of eight years, its metabolized form, DDE, can slowly build up in fatty tissues. Pelicans, along with other species at the top of aquatic food chains, are especially susceptible to this bioaccumulation because the amount of the contaminant is magnified along each successive stage in the chain.

Soon, DDT and other pesticides in the organochlorine family such as dieldrin, endrin, and chlordane became the prime suspects in the Louisiana dieback. Given that the Mississippi River drains the agricultural plains in the nation's heartland and that organochlorines, as highly effective as they were, had become the pesticide of choice in U.S. agribusiness and suburban backyards alike, this causal scenario and subsequent experiments made for a far better fit than any of the other theories.

Two eggs in a nest

Rather than killing the birds directly through toxicity, experimental studies showed that organochlorines create two particular enzymatic reactions that thwart brown pelicans' ability to reproduce. One reaction increases the enzyme that, in turn, can slow or halt the steroid production crucial to eggshell formation. The other reaction decreases the enzyme that triggers the formation of calcium carbonate. This compound, found in the bone-building calcium supplements we humans take to prevent osteoporosis, also provides rigidity to the eggshells of most bird species. The resulting loss of eggshell thickness-over 25% from the 1947, pre-DDT era levels in some field observations-was enough that the pelicans would destroy their eggs as they instinctually sat within their nests to incubate and protect them.

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A Tentative Return

By 1968, a brown pelican restocking program was in place in Louisiana. A joint effort between the Louisiana Department of Wildlife and Fisheries and the Florida Game and Fresh Water Fish Commission, the program called for the transport of fledglings from Florida's peninsula to three release sites in southeastern Louisiana: Queen Bess Island, Isle Aux Pitre, and North Island. Along with the reintroduction of the Florida juveniles to traditional nesting areas in Louisiana, the program monitored reproductive success, survival rates, and environmental contaminants. Over the course of the next twelve years, an average of 110 birds a year would be transplanted, with special attention being paid to the cultivation of the nesting sites formerly found on Queen Bess and North Islands. This readoption of the nesting grounds was encouraged by clipping some of the birds' wings so that flightless, resident groups could be established that would discourage the free-ranging birds from straying too far.