Populations Globally, pelican populations are adversely affected by these main factors: declining supplies of fish through overfishing or water pollution, destruction of habitat, direct effects of human activity such as disturbance at nesting colonies, hunting and culling, entanglement in fishing lines and hooks, and the presence of pollutants such as
DDT and
endrin. Most species' populations are more or less stable, although three are classified by the
IUCN as being at risk. All species breed readily in zoos, which is potentially useful for conservation management. '',
Tortuga Bay, Island of Santa Cruz, Galápagos The combined population of brown and Peruvian pelicans is estimated at 650,000 birds, with around 250,000 in the United States and Caribbean, and 400,000 in Peru. The
National Audubon Society estimates the global population of the brown pelican at 300,000. Numbers of brown pelican plummeted in the 1950s and 1960s, largely as a consequence of environmental DDT pollution, and the species was listed as endangered in the US in 1970. With restrictions on DDT use in the US from 1972, its population has recovered, and it was delisted in 2009. The Peruvian pelican is listed as near threatened because, although the population is estimated by
BirdLife International to exceed 500,000 mature individuals, and is possibly increasing, it has been much higher in the past. It declined dramatically during the 1998
El Niño event and could experience similar declines in the future. Conservation needs include regular monitoring throughout the range to determine population trends, particularly after El Niño years, restricting human access to important breeding colonies, and assessing interactions with fisheries. The spot-billed pelican has an estimated population between 13,000 and 18,000 and is considered to be near threatened in the IUCN Red List of Threatened Species. Numbers declined substantially during the 20th century, one crucial factor being the eradication of the important
Sittaung valley breeding colony in Burma through deforestation and the loss of feeding sites. The chief threats it faces are from habitat loss and human disturbance, but populations have mostly stabilised following increased protection in India and Cambodia. The pink-backed pelican has a large population ranging over much of
sub-Saharan Africa. In the absence of substantial threats or evidence of declines across its range, its conservation status is assessed as being of least concern. Regional threats include the drainage of wetlands and increasing disturbance in southern Africa. The species is susceptible to
bioaccumulation of toxins and the destruction of nesting trees by logging. The American white pelican has increased in numbers, However, whether its numbers have been affected by exposure to pesticides is unclear, as it has also lost habitat through wetland drainage and competition with recreational use of lakes and rivers. The Dalmatian pelican has a population estimated at between 10,000 and 20,000 following massive declines in the 19th and 20th centuries. The main ongoing threats include hunting, especially in eastern Asia, disturbance, coastal development, collision with overhead power lines, and the over-exploitation of fish stocks. It is listed as near threatened by the IUCN Red List of Threatened Species as the population trend is downwards, especially in Mongolia, where it is nearly extinct. However, several European colonies are increasing in size and the largest colony for the species, at the
Small Prespa Lake in Greece, has reached about 1,400 breeding pairs following conservation measures. Widespread across Australia, Overall population numbers fluctuate widely and erratically depending on wetland conditions and breeding success across the continent. The species is assessed as being of least concern.
Culling and disturbance Pelicans have been persecuted by humans for their perceived competition for fish, despite the fact that their diet overlaps little with fish caught by people. Great white pelicans on Dyer Island, in the Western Cape region of South Africa, were culled during the 19th century because their predation of the eggs and chicks of
guano-producing seabirds was seen to threaten the livelihood of the guano collectors.
Poisoning and pollution DDT pollution in the environment was a major cause of decline of brown pelican populations in North America in the 1950s and 1960s. It entered the oceanic
food web, contaminating and accumulating in several species, including one of the pelican's primary food fish – the
northern anchovy. Its
metabolite DDE is a reproductive
toxicant in pelicans and many other birds, causing eggshell thinning and weakening, and consequent breeding failure through the eggs being accidentally crushed by brooding birds. Since an effective ban on the use of DDT was implemented in the US in 1972, the eggshells of breeding brown pelicans there have thickened and their populations have largely recovered. In the late 1960s, following the major decline in brown pelican numbers in Louisiana from DDT poisoning, 500 pelicans were imported from Florida to augment and re-establish the population; over 300 subsequently died in April and May 1975 from poisoning by the pesticide endrin. About 14,000 pelicans, including 7,500 American white pelicans, perished from
botulism after eating fish from the
Salton Sea in 1990. As waterbirds that feed on fish, pelicans are highly susceptible to
oil spills, both directly by being oiled and by the impact on their food resources. A 2007 report to the California Fish and Game Commission estimated that during the previous 20 years, some 500–1,000 brown pelicans had been affected by oil spills in California. Where pelicans interact with fishers, through either sharing the same waters or scavenging for fishing refuse, they are especially vulnerable to being hooked and entangled in both active and discarded fishing lines.
Fish hooks are swallowed or catch in the skin of the pouch or webbed feet, and strong
monofilament fishing line can become wound around bill, wings, or legs, resulting in crippling, starvation, and often death. Local rescue organisations have been established in North America and Australia by volunteers to treat and rehabilitate injured pelicans and other wildlife.
Parasites and disease As with other
bird families, pelicans are susceptible to a variety of
parasites.
Avian malaria is carried by the
mosquito Culex pipiens, and high densities of these biting insects may force pelican colonies to be abandoned.
Leeches may attach to the
vent or sometimes the inside of the pouch. A study of the parasites of the American white pelican found 75 different species, including
tapeworms,
flukes,
flies,
fleas,
ticks, and
nematodes. The brown pelican has a similarly extensive range of parasites. The nematodes
Contracaecum multipapillatum and
C. mexicanum and the
trematode Ribeiroia ondatrae have caused illness and mortality in the
Puerto Rican population, possibly endangering the pelican on this island. Many pelican parasites are found in other bird groups, but several
lice are very
host-specific. In May 2012, hundreds of Peruvian pelicans were reported to have perished in
Peru from a combination of starvation and
roundworm infestation. ==Symbolism and cultural significance==