Brown Pelicans

Family:
Species: 
Common name:
Pelecanus
Pelecanus occidentalis
Brown Pelican


Brown pelicans, although the smallest of the pelican family are still relatively large birds (up to 8 pounds). They are about 112-137cm long, and have a wingspan of approximately 2 meters (7 ft). They are familiar to us because of their huge pouched bill.

There are 6 subspecies of Brown Pelican, they are all similar in appearance, but are distinguished by the geographical distribution, and by slight differences in plumage and size. STARSHIP has encountered the Eastern, Californian and most recently the Caribbean subspecies. Soon we will hopefully also come across the Galapagos subspecies.

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DESCRIPTION

Regarding plumage, both sexes are alike, although males are on average slightly larger. Adults have silvery grey-brown body plumage, with blackish flight feathers and a yellow and white head with chestnut nape and hind neck. In adult birds the plumage plays a significant role in communication. During the breeding period, prior to nesting, the hind neck becomes vibrant dark reddish brown. In the winter or during the non-breeding period the head and neck are mainly white.

Brown Pelicans have yellow eyes and dark blue-grey facial skin. Their bill is grey or yellowish, with a scarlet cast on the distal portion. Their pouch (called the gular pouch) varies from red to greenish or blackish and their legs and feet are blue-grey to black.

Juveniles are generally brown above and white below and it takes them about three years to attain their adult plumage.

HABITAT

Brown Pelicans are found on both coasts of Tropical North and South America. They are true marine pelicans and feed by diving from the wing. They are rarely seen inland or far out to sea. They prefer shallow estuarine waters for fishing and will seldom venture more than 20 miles out to sea, except to take advantage of particularly good fishing conditions. They use beaches, sand bars, sand spits, for roosting at night and also for loafing about during the day. Harbours are also favourite daytime haunts for Brown Pelicans.

They are social birds, breeding feeding and flying together. Their flight consists of heavy flaps, followed by a long glide often low to the surface of the water. They gain height by soaring on outstretched wings in thermals. They are often ungainly when landing or taking off, requiring a run across the surface to become airborne.

Brown Pelicans usually fish together in small flocks, driving fish into shallows near beaches or reefs and then scooping them up with open pouches. We watched a group if 5 doing this at Los Roques. They also feed by plunge diving from flight, either at a shallow angle as they skim the water or diving steeply from high overhead. They can store food in their distensible gular pouch until it is ready to consume. Although sometimes they risk loosing their catch to Laughing gulls who torment them unmercifully until they open their beaks.

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Brown Pelican diving for fish

REPRODUCTION

Brown Pelicans breed from March to November. The Caribbean subspecies begins nesting between May and August, which explains why we have seen many adults decked out in their breeding plumage, however the peak nesting season is generally during September through to November. Preferred nesting sites are landward on small coastal islands, which provide some degree of protection from mammalian predators, surf and storms.

The courtship behavior is confined to the nest site. During courtship the male circles the motionless female, lifting his wings slightly and tilting his head far back. He then carries nesting materials to the female who builds the nest. The nests are usually built in small mangrove tress, where they can be anything from 1 to 10m above the high tide mark, but ground nesting also occurs. Ground nests vary from almost nothing - bare sand, rock, or mud lumps, to well-constructed nests of sticks, reeds, grasses, seaweed, and palmetto leaves. Along populated coasts pelicans may even pick up and use rubbish. Nests in trees are made of similar materials although they are more firmly constructed. The typical clutch size for the brown pelican is 3 eggs (each about 70x45mm) and the male and female share the brooding and feeding of the 2-3 chalky white chicks. The first chick to hatch is the first egg laid, this chick is correspondingly larger than his siblings when they hatch and as a result gets more of the food. When food is scarce, such as during El Nino events the third siblings often starve to death (Dr. E.A. Schreiber, pers.com.). As the chicks develop the upper body and neck parts turn grey brown, but the belly remains white. They retain this plumage for about 3-4 years.

Brown Pelicans are thought to be long-lived. They probably live commonly to 25 years (Dr. E.A. Schreiber, op.cit.) and one bird captured in Florida was found have been tagged 31 years previously

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Juvenile Brown Pelican in flight

STATUS

The Brown Pelican was listed as endangered throughout its range in 1970. It had previously been a common site along US coasts, for example, but in the 1960,s and 70,s a drastic decline in the population occurred.

This was the result of the extensive use of pesticides such as DDT, the residues of which (DDE and DDD) accumulate in plants and animals. These residues then make their way up the food chain from plankton, into small fish and eventually into the larger fish that are the Pelicans primary food source. The process of biomagnification means that the contaminant is concentrated many times over in animals higher up in the food chain. Accumulation of pesticide residues in fish caused thinning of the eggshells and reproductive failure in Brown Pelicans. Since Brown Pelicans incubate their eggs by standing on them with their highly-vascularised feet any loss of structural strength means that the eggs are instantly crushed, regardless of how delicately the bird steps onto the egg. The process of eggshell thinning began soon after 1947, when DDT was widely used in North America.

DDT has also been proven to cause failure to lay eggs and increased embryonic mortality.

Not only are the eggs and reproductive capacity of the birds damaged by pesticide residues, the birds themselves can be poisoned. DDT can remain stable in the environment for years and is stored in the body fat. During times of stress and malnutrition, such as pronounced El Nino events for example, when the ocean warms and seabirds cannot find enough food, the fatty acid deposits are broken down and metabolized and the poisons are released into the birds system.

In 1972 the Environmental Protection Agency placed a ban on the use of DDT in North America. Since that time the environmental residues have decreased in most areas. There has been a subsequent and corresponding increase in the eggshell thickness and the reproductive success of the Brown Pelican. The restoration of the Brown Pelican in North America is somewhat of a success story. A restoration project was implemented from 1968 to 1980 by the Louisiana Department of Wildlife and Fisheries, and the Fresh Water Fish Commission. Brown Pelicans were reintroduced at several locations, they went on to breed and the numbers are steadily increasing, such that the Brown Pelican is now common in many coastal North American waters.

However that said, DDT is still in use all over the world and remains a threat, not only to Brown Pelicans but also to Peregrine Falcons, Ospreys, many Fish-eating eagles and Cormorants. The Environmental protection agency now lists DDT, which has diminished in the environment but is still widely present, as a probable human carcinogen.

There are other factors affecting the Brown Pelican, particularly the Caribbean subspecies. Human disturbance can be significant, poaching of eggs, young and adults occurs, and since Brown Pelicans are sensitive at their breeding localities they can loose their eggs to scavenging Laughing Gulls and other predators if disturbed. Mortalities also result from birds being caught on fishhooks and subsequently entangled in the line. Hurricanes, storms can devastate nesting colonies and periodic El Nino events may cause food scarcity. Although pesticide residues are not yet considered high enough in the Caribbean to be hazardous, the Brown Pelicans environment is also under threat; loss or degradation of mangrove forests reduces the feeding grounds and breeding areas. The last rough estimate of the population in the Caribbean was 1,500 to 1,800 birds (Jaime Collazo, US Fish and Wildlife Service, 1991).

References/Acknowledgements

U.S. Fish and Wildlife. Selected Vertebrate Endangered Species of the Seacoast of the United States. Brown Pelican: Eastern and Californian Subspecies, FWS/OBS-80/01.40. March 1980

Thanks to Dr E.A. Schreiber, in the Bird Department of the National Museum of Natural History, (Washington DC) for her comments.

Thanks to Megan Robertson (South Cheshire College, Cheshire, UK) and Helen Tipper and her school class (Deacons School, Peterborough, UK) for searching the Web for reference material.

This page will be updated if I receive further information

Dr. Janet Sumner-Fromeyer