II. HABITAT & DISTRIBUTION
P. occidentalis is found on both coasts of North and South America (Harrison 1996). Its range extends along the Pacific coast from Washington south to Peru, including the Galapagos Islands, and on the Atlantic coast from North Carolina throughout the Caribbean to Brazil. Occasionally, birds are spotted as far north as British Columbia and Nova Scotia on the Pacific and Atlantic coasts, respectively (Farrand 1983). The species is common in the southeast United States and is the state bird of Louisiana (Terres 1980).
Populations are found around beaches, bays and a variety of habitats in tidal estuaries (Farrand 1983). Brown pelicans are rarely seen inland except accidentally as the result of hurricanes and other strong storms (Terres 1980).
Indian River Lagoon (IRL) Distribution:
Brown pelicans are found throughout the IRL in all habitats. Large groups of birds tend to gather near marinas, jetties and other popular fishing spots to feed on scraps as fishers clean their catch.
III. LIFE HISTORY & POPULATION
Age, Size, Lifespan:
Although it is considered the smallest member of the pelican family (Terres 1980), P. occidentalis is a large marine bird often measuring over 1 m in length (Harrison 1996) with a wingspan of nearly 2.3 meters (Farrand 1983) and a total weight of about 8 pounds (3.6 kg). (Terres 1980). Males average a slightly larger body size than females (Terres 1980).
Lifespan varies with environmental conditions, food availability and other factors. Some banded individuals have been documented to exceed 31 years of age (Terres 1980).
Brown pelicans are quite abundant along the east coast of the U.S., although populations in parts of the Gulf of Mexico, along the Pacific coast and in Central and South America are still continuing to recover from past populations declines (see 'Threats & Conservation' below).
P. occidentalis is a social species, gregarious throughout the year with colonial breeding behavior (Harrison 1996). Breeding dates vary with location, but most populations reproduce from March to August. At the Pelican Island National Wildlife Refuge in the IRL, breeding continues nearly year-round (Terres 1980).
During the breeding season, nests in trees and bushes are constructed from straw or grass placed on mounds of sticks woven onto a supporting branch (Terres 1980). Ground nests are comprised of feather-lined impressions protected with a 10-25 cm rim of soil and debris. Pelicans usually lay 2-3 eggs at a time, incubating them for a period of 28-30 days (Terres 1980). Chicks in ground nests venture out by walking after approximately 35 days, while those in trees wait for about 65-80 days to fly from the nest.
Hybrids of brown and white pelicans are possible, and one such offspring was on display at the National Zoo in Washington, D.C. in 1937 (Terres 1980).
Adult brown pelicans are silent, rarely emitting a low croak, while hatchlings frequently squeal (e.g. Peterson 1980).
IV. PHYSICAL TOLERANCES
The natural range of the brown pelican is concentrated mainly in warm temperate to tropical climate zones, suggesting that the species has a minimum thermal tolerance. Additionally, Schreiber (1980) suggested that nesting times coincided with warmer temperatures, and found that tropical populations experience longer breeding seasons when compared to their counterparts at higher latitudes.
As mentioned above, the brown pelican is a coastal bird, feeding and nesting in and around marine and estuarine waters. Although the bird likely has a tolerance for all salinities, it is rarely seen in freshwater environments (Farrand 1983).
V. COMMUNITY ECOLOGY
The brown pelican feeds exclusively on marine fishes and occasional crustaceans by diving into the water head-first from heights of 6 to over 15 meters, capturing up to 4 pounds of prey daily with its long, slender beak (Farrand 1983; USFWS 1995; Harrison 1996). Studies have suggested that the height and angle of these dives vary with the age and skill level of the bird, and dive paths are altered to reduce glare on the surface of the water that may hinder catch success (Carl 1987). The large pouch below the bill acts as dip net to catch prey, but also holds fish for consumption until the water, as much as three gallons, is squeezed out. Once the water is removed, the prey is swallowed. In addition to catching and holding prey, the pouch also serves as a cooling mechanism for the bird in warm weather and a feeding trough for young (USFWS 1995).
Little information is available concerning predators of the brown pelican. Due to their size and long sturdy bill, it is unlikely that adult birds are regularly preyed upon. However, birds of prey, alligators or large mammals could potentially consume eggs and hatchlings.
Like many other bird species, the brown pelican acts as a terminal or final host for several parasites acquired from a variety of prey items, including the parasitic worms Petagiger sp., Echinochasmus sp., Phagicola longus, Mesostephanus appendiculatoides, Contracaecum multipapillatum, and C. bioccai acquired from the black mullet, Mugil cephalus, the silver mullet, M. curema and other fish prey (Grimes et al. 1989; Zamparo et al. 2005; Mattiucci et al. 2008). Most of these parasites infect the gut, with some imposing minimal negative impacts on the pelican, while others are more virulent or increase the probability of infections by secondary pathogens (e.g. Grimes et al. 1989).
Although there are no obligate associations documented between the brown pelican and other species, P. occidentalis is commonly found alongside other organisms from the seagrass beds, mangrove forests, tidal flats and other ecosystems in which it resides. For more extensive information on these environments and their associated species found in the IRL, please visit the Habitats of the IRL page.
VI. SPECIAL STATUS
The brown pelican is listed as a species of special concern based on its vulnerability to habitat modification and human disturbances (e.g. Schreiber & Mock 1988; Klein et al. 1995). These factors may threaten the species in the absence of effective management and conservation strategies (FWCC 2009).
Species of Special Concern, Criterion #1 (SSC 1)
Threats & Conservation:
Once thriving throughout its range, populations of the brown pelican began to decline in the late 19th and early 20th centuries as the result of plume hunting and slaughter by fishermen who viewed the birds as competition for valuable catch (USFWS 1995). In 1903, President Theodore Roosevelt designated Pelican Island on the Indian River Lagoon as the first national wildlife refuge, reducing the threat of plume hunters in the area. Further protection was established by the passage of the Migratory Bird Treaty Act of 1918, and enhanced when studies revealed that brown pelicans were not detrimental to commercial fish stocks.
Unfortunately, pelican populations began to decline again in the mid 20th century from poor reproductive success linked to the widespread use of toxic pesticides like DDT and dieldrin. Studies found that these chemicals were transported by water (irrigation and/or rain) from treated agricultural areas into pelican feeding grounds located in nearby estuaries and coastal waters (Terres 1980; USFWS 1995). Pesticides ingested from contaminated prey items resulted in disruption of calcium metabolism in pelicans, leading to eggshell thinning and subsequent loss of young from egg damage. In 1970, the U.S. Fish and Wildlife Service listed the brown pelican as an endangered species, which was followed shortly by the banning of DDT and the restriction of similar pesticides by the Environmental Protection Agency in 1972. By 1985, improved breeding success led to population growth that allowed the brown pelican to be removed from the Endangered Species List in Alabama, Florida and along the entire Atlantic coast (USRWS 1995). In November 2009, the bird was delisted as an endangered species across the remainder of its distribution (Federal Register 2009).
Recovery efforts are ongoing to increase pelican populations across their natural range. These programs include continued banding and census of existing birds in order to plot migration patterns and gather data on lifespan and growth rates, as well as the patrolling of rookeries and sanctuaries to minimize human disturbance to nesting sites in these designated areas.
VII. LITERATURE CITED & OTHER USEFUL REFERENCES
Carl, RA. 1987. Age-class variation in foraging techniques by brown pelicans. The Condor 89: 525-533.
Farrand Jr., J (Ed.). 1983. The Audubon Society Master Guide to Birding Volume 1: Loons to Sandpipers. Alfred A. Knopf. New York. USA. 447 pp.
Federal Register. 2009. Endangered and Threatened Wildlife and Plants; Removal of the Brown Pelican (Pelecanus occidentalis) from the Federal List of Endangered and Threatened Wildlife; Final Rule. Department of the Interior. Fish and Wildlife Service. Federal Register Vol.17, No. 20. Online at http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2009_register&docid=fr17no09-14 (Date accessed 08/07/2010).
FNAI. 2001. Field Guide to the Rare Animals of Florida. Florida Natural Areas Inventory. Online at http://www.fnai.org/fieldguides.cfm (Date accessed 08/07/2010).
FWCC. 2009. Florida’s endangered species, threatened species, and species of special concern. Florida Fish and Wildlife Conservation Commission. Online at http://myfwc.com/WILDLIFEHABITATS/imperiledSpp_index.htm (Date accessed 08/07/2010).
FWCC. 2003. Florida’s Breeding Bird Atlas: A Collaborative Study of Florida’s Birdlife. Florida Fish and Wildlife Conservation Commission. Online at http://www.myfwc.com/bba/ (Date accessed 08/07/2010).
Harrison, P. 1996. Seabirds of the World: A Photographic Guide. Princeton Univ. Press. Princeton, NJ. USA. 317 pp.
Kale II, HW & DS Maehr. 1990. Florida’s Birds. Pineapple Press. Sarasota, FL. USA. 288 pp.
Klein, ML, Humphrey, SR & HF Percival. 1995. Effects of ecotourism on distribution of waterbirds in a wildlife refuge. Conserv. Biol. 9: 1454-1465.
Grimes, J, Suto, B, Greve. JH & HF Albers. 1989. Effect of selected anthelmintics on three common helminthes in the brown pelican (Pelecanus occidentalis). J. Wildlife Diseases 25: 139-142.
Kushlan, JA & PC Frohring. 1985. Decreases in the brown pelican population in southern Florida. Colonial Waterbirds 8: 83-95.
Mattiucci, S, Paoletti, M, Olivero-Verbel, J, Baldiris, R, Arroyo-Salgado, B, Garbin, L, Navone, G & G Nascetti. 2008. Contracaecum bioccai n. sp. from the brown pelican Pelecanus occidentalis (L.) in Columbia (Nematoda: Anisakidae): morphology, molecular evidence and its genetic relationship with congeners from fish-eating birds. Syst. Parasitol. 69: 101-121.
Peterson, RT. 1980. A Field Guide to the Birds: A Completely New Guide to All the Birds of Eastern and Central North America. Houghton Mifflin. Boston, MA. USA. 384 pp.
Schreiber, RW. 1980. Nesting chronology of the eastern brown pelican. The Auk 97: 491-508.
Schreiber, RW & PJ Mock. 1988. Eastern brown pelicans: What does 60 years of banding tell us? J. Field Ornithol. 59: 171-182.
Schreiber, RW & EA Schreiber. 1983. Use of age-classes in monitoring population stability of brown pelicans. J. Wildl. Manage. 47: 105-111.
Terres, JK. 1980. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf. New York. USA. 1109 pp.
USFWS. Brown Pelican: Endangered Species Success Story. Biologue Series. U.S. Fish and Wildlife Service.
Zamparo, D, Overstreet, RM & DR Brooks. 2005. A new species of Petasiger (Digenea: Echonostomiformes: Echinostomatidae) in the brown pelican, Pelecanus occidentalis, (Aves: Pelecaniformes: Pelecanidae), from the Area de Conservación Guanacaste, Costa Rica. J. Parasitol. 91: 1465-1467.
Report by: LH Sweat,
Smithsonian Marine Station at Fort Pierce
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Page last updated: 28 September 2010
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