Pelecanus occidentalis

Formerly included P. thagus Molina, 1782 [Peruvian Pelican], now considered distinct (e.g. Sibley and Monroe 1990, Ridgely and Greenfield 2001) on the basis of much larger size, differences in color of plumage and soft parts (Wetmore 1945), and absence of interbreeding (Banks et al., 2008).

Large range, extending from North America to South America; most U.S. populations have been stable or increasing in recent years; population status in much of Central and South America is not well known, but the species may be moderately to highly threatened throughout much of the range, mainly as a result of environmental pollution and disturbance by humans; subject to unexplained population fluctuations even where doing well overall.

Breeding range extends along the Pacific coast from southern California to South America and along Atlantic, Gulf, and Caribbean coasts from Maryland south to Florida and westward to southern Texas, plus the Bahamas, West Indies, Yucatan Peninsula, and off Venezuela and the Caribbean coast of Colombia. During the nonbreeding season, brown pelicans range in Pacific coastal waters north to southern British Columbia (after breeding, before winter); in western North America, the species winters mainly from California south; in the southeastern U.S., the primary winter range includes Florida and the Gulf Coast.

Subspecies CAROLINENSIS: breeds locally in Maryland and Virginia and south to Florida (primary nesting range), also locally in Louisiana (where reintroduced) and in central coastal Texas; breeds locally also off northeastern Yucatan and Belize, and ranges southward through coastal Honduras and Costa Rica to Panama, where local breeding occurs off the Pacific coast; vagrants wander north to New England and occur casually inland to the Great Lakes and Great Plains states (Johnsgard 1993). Breeds also in the Bahamas (Sprunt 1984) (extirpated, according to Johnsgard 1993). Ranges throughout breeding range and along eastern shores of Mexico south along Central America to the Caribbean coasts of Colombia and Venezuela, and through the Greater and Lesser Antilles to Trinidad; and on the Pacific coast of Central America (AOU 1957).

Subspecies CALIFORNICUS: breeds along Pacific coast in southern California (Anacapa Island), and in Mexico on islands off Baja California and on islands in the Gulf of California (south to Isabella and the Tres Marias Islands); possibly locally along the coast of Sonora and Sinaloa; vagrants have occurred north to British Columbia and Idaho (Johnsgard 1993).

Many occurrences are distributed throughout the coastal range in North, Central, and South America.

This species was nearly extirpated from North America between the late 1950s and early 1970s when pesticides entering the marine food web caused major population declines. The pesticide endrin killed pelicans directly, whereas DDT reduced reproductive success by causing pelicans to lay thin-shelled eggs that broke during incubation.

Populations are extremely vulnerable to chemical/pesticide pollution, which can result in eggshell thinning (reproductive failure) (Anderson and Hickey 1970, Blus et al. 1974), and presumably lethal poisoning. Populations (especially in California, Texas, and Louisiana) were decimated in the U.S. by pesticides (DDT and related compounds) in the 1950s and 60s. In the U.S. Caribbean, 7% of the pelican population in 1982 died as a result of fish die-offs in connection to chemical runoffs (e.g., organophosphates). Other threats include disturbance of nesting birds by humans (reduces reproductive success), declining fish (food) populations, increased turbidity (e.g., from dredging, resulting in reduced visibility of prey); oil and other chemical spills, entanglement in fishing gear, shooting, extreme weather conditions (freezing of soft parts, destruction of nest sites by hurricanes, storms), disease, and parasitism.

Human disturbance (e.g., recreational boating, poaching) not only disrupts reproductive success (Anderson and Keith 1980; Schreiber 1979), but may affect distribution patterns and age structure of pelicans using roosting sites during the nonbreeding season (Jaques and Anderson 1987). Habitat degradation affects both roosting and nesting patterns. On the Gulf Coast, nesting efforts have failed because nesting sites are susceptible to flooding as a result of continued site erosion (McNease et al. 1992).

Subspecies CALIFORNICUS: Declined greatly due to effects of pesticide contamination in the 1950s and 1960s. In Southern California threatened by pollution (primarily pesticides in food fishes, also oil), human disturbance of breeding colonies, loss or serious decline of food fishes due to human over-fishing (e.g., of anchovies); loss of post-breeding roost sites, fishing gear entanglement, and bacterial infection resulting from overcrowding at fish disposal areas in harbors (California Department of Fish and Game 1990). Human disturbance has decreased nesting success on Islas los Coronados, Mexico (Anderson 1988) and virtually extirpated the breeding colony (California Department of Fish and Game 1990). Southern populations in Mexico have faced problems associated with human disturbance and overexploitation of prey (e.g., sardines), yet they remain stable (D. W. Anderson, pers. comm.).

U.S. Caribbean: contaminant levels and availability of nesting habitat are not limiting or affecting the population at present. See Williams et al. (1992) for an account of die-offs that have been observed in Puerto Rico and the Virgin Islands; apparent causes include pesticides, botulism, and unknown factors. In the tropics and subtropics, coastal development and incidental take (e.g., artisanal fishing) is a problem and represents a major threat to the continued availability of mangrove habitat. Close to 91% of all roosting and nesting habitat utilized in the U.S. Caribbean are fringe and overwash mangroves. Fringe mangroves are particularly important to the feeding ecology of pelicans because they provide nutrient inputs and cover for the associated marine community, including food fishes. Both mangrove types are very sensitive to human-created stress such as deforestation, filling and extractions in the salt flats, sedimentation, and oil spills (Cintron and Schaeffer-Novelli 1983). Siltation caused by erosion could be adversely impacting coral reefs, seagrass beds, and mangrove forests (Cintron and Schaeffer-Novelli 1983, Velazco et al. 1985).