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. thumb|Pelecanus occidentalis, 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.
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. thUmb|pEleCanus oCCidentaLis, 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.