Adaptations of the Brown Pelican in Tropical Dry Forests

Nesting Sites

• Brown pelicans will utilize swaths of tropical dry forest for nesting purposes, particularly those situated on offshore islands. Such isolated land masses offer greater protection from terrestrial nest-predators like raccoons and snakes. The birds will nest on bare ground, but usually prefer an arboreal setting. Often nest sites are actually in belts of mangrove forest fringing the seaward front of the woodlands or scrub, but the huge birds also select interior trees. Figs, gumbo-limbo and sea-grape are among the trees and shrub-trees supporting pelican nests in the Caribbean region. On the rough face of Bolaños Island off the northwestern coast of Costa Rica, brown pelicans share breeding space with magnificent frigatebirds in contorted dry groves of paira, fraginipani and lancewood. Such tree nests are often 6 to 40 feet above the shoreline, according to the U.S. Fish and Wildlife Service.

Breeding Behavioral Adaptations

• Male pelicans typically choose a likely nest site, then attract a receptive female with a head-swaying routine. The female constructs the nest with branches, twigs, leaves and grasses supplied by the male. Brown pelicans may take advantage of seasonal cycles of food availability to time their nesting. Pelicans breeding on Taboga Island in the Bay of Panama, which includes tracts of tropical dry forest, seemed to take advantage of the patterns of marine upwellings offshore, which increase nutrients at the surface, according to a 1984 study. Brown pelicans nesting on the Channel Islands off southern California -- cloaked in Mediterranean-zone chaparral scrub not dissimilar from certain tropical dry-forest ecosystems -- are highly dependent on the availability of northern anchovies and Pacific sardines during the nesting season.

Feeding

• Brown pelicans have evolved a highly specialized and dramatic feeding style quite distinct from other pelicans, which tend to fish by paddling at the surface and sieving with their pouches. Brown pelicans perform spectacular aerial dives from as high as 60 feet above the water. The extreme physical impact upon hitting the ocean is moderated by special air sacs under the pelican's skin. Scooping up over two gallons of water with their expandable pouches, they expel the liquid and toss back the small fish thus captured. While nesting, brown pelicans tend to fish around 12 miles or less from their breeding location, though at other times of the year they will forage substantially farther out to sea. The birds require above-water perches for resting and drying out between fishing bouts.

Migration

• While many pelicans in the tropical dry-forest zone are relatively resident, others from higher latitudes may migrate into the region to breed. Some brown pelicans on the Pacific Coast winter and nest off southern California, Mexico and Central America, then head northward along Oregon, Washington and British Columbia near shore waters to forage.