It nests in colonies in secluded areas, often on islands, vegetated land among sand dunes, thickets of shrubs and trees, and mangroves.

In 1903, Theodore Roosevelt set aside the first National Wildlife Refuge, Florida's Pelican Island, to protect the species from hunters.

The brown pelican was described by Swedish zoologist Carl Linnaeus in the 1766 12th edition of his Systema Naturae, where it was given the binomial name of Pelecanus occidentalis.

The upper sides of the neck have white lines along the base of the gular pouch, and the lower foreneck has a pale yellowish patch.

It has a silvery gray mantle, scapulars, and upperwing coverts (feathers on the upper side of the wings), with a brownish tinge.

While usually restricted to coastal regions, brown pelicans occasionally wander inland, and there are records of vagrant individuals across much of the interior of North America.

Rare inland vagrants, generally caused by hurricanes or El Niño phenomena, have been reported from the Colombian Andes.

[34] In level flight, brown pelicans fly in groups, with their heads held back on their shoulders and their bills resting on their folded necks.

[40] Other fish preyed on with some regularity includes pigfish, pinfish, herring, sheepshead, silversides, mullets, sardines, minnows, and topminnows.

[42] Non-fish prey includes crustaceans, especially prawns, and it occasionally feeds on amphibians and the eggs and nestlings of birds (egrets, common murres and its own species).

[27] At the proposed nest site, major courtship displays such as head swaying, bowing, turning, and upright (standing on its legs without any support) are performed by both the sexes.

[53] They are usually built by the female from reeds, leaves, pebbles, and sticks,[55] and consist of feather-lined impressions protected with a 10 to 25 cm (3.9 to 9.8 in) rim of soil and debris.

[24] In the 8- to 10-month period during which they are cared for, the nestling pelicans are fed by regurgitated, partially digested food of around 70 kg (150 lb) of fish.

Also, South American sea lions and unidentified large sharks have been observed to prey on adult brown pelicans by seizing them from beneath while the birds are sitting on ocean waters.

[61] The brown pelican is now a staple of crowded coastal regions and is at some risk by fishermen (monofilament fishing line and hooks) and boaters.

In 1998, American conductor David Woodard performed a requiem for a California brown pelican on the seaward limit of the berm of a beach where the animal had fallen.

[78][79]: 152–153  In the 2003 Disney/Pixar film Finding Nemo, a brown pelican (voiced by Geoffrey Rush in an Australian accent) was illustrated as a friendly, virtuous talking character named Nigel.

[80][a] Since 1988, the brown pelican has been rated as least concern on the IUCN Red List of Endangered species based on its large range—greater than 20,000 km2 (7700 mi2)—and an increasing population trend.

[84] Starting in the 1940s with the invention and extensive use of pesticides such as DDT, the brown pelican population had drastically declined due to a lack of breeding success.

By the 1960s, it had almost disappeared along the Gulf Coast and, in southern California, it had suffered almost total reproductive failure, due to DDT usage in the United States.

[6] Between 1968 and 1980, the Louisiana Department of Wildlife and Fisheries' reintroduction program re-established the brown pelican, and its population numbers in California and Texas were restored due to improved reproduction and natural recolonization of the species.

Although the United States Gulf Coast populations in Louisiana and Texas are still listed as endangered, they were recently estimated in 2009 about 12,000 breeding pairs.

[42] Fluctuations in sardine populations have largely been attributed to bottom-up control, primarily including climate variability and ocean temperature.

[87] The significant decrease in pacific sardine population can be linked to the levels of nitrogen within their habitat, a limiting factor in plankton production.

[87] Pacific sardines in the California current system rely on wind driven upwelling to push cooler, nitrogen rich waters towards the surface, maintaining a sustainable, nutrient abundant environment.

[87] Continued environmental disruptions, such as El Niño, rising ocean temperatures, and increased commercial fishing, have drastic effects on nutrient cycling within the California current system, leading to lasting impacts on Pacific sardine productivity and reproductive success.

[90] Environmental changes tend to have fast acting impacts on marine bird populations due to the simplicity of their trophic cascade, allowing for complex, long term trends in ecosystem health and resources to be easily realized and tracked.

[88] This indicates that even when fisheries are not seeing signs of declining sardine abundance, brown pelicans may have already been affected to the point of locating other food sources.

[88] This availability of sardines may decline even further during El Niño anomalies, when thermoclines prevent brown pelicans from reaching their prey.

[88] Although brown pelicans serve as an important indicator species for fisheries, declining sardine abundance due to both climate changes and overfishing have huge implications on overall ecosystem health, within or outside the individual trophic cascade.