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.
- Part One
- Part Two
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.
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!
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
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.
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.
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
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