Brown Pelican

Range

Habitat

Food

Reproduction

Behavior

Status

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.