Living Sanibel: Brown Pelicans
As you travel up and down the coast, it is impossible not to spot this large, easily recognized bird feeding on the threadfin herring and glass minnows that gather along the shoreline and in the shadows cast by the numerous bridges ferrying you across to the barrier islands. What is harder to grasp is that the ubiquitous brown pelican was fast approaching extinction in the 1960s and 0s.
Widespread use of DDT to control the Florida mosquito population altered the calcium metabolism in pelicans and other birds, causing them to produce eggs with shells too thin to support the embryo to maturity. In nearby Louisiana (where, ironically, the pelican is the state bird) the population completely collapsed because of the overuse of these pesticides. Louisiana had to import Florida pelicans through the 1980s to help rebuild its decimated flocks. Today, they are once again rebounding from yet another manmade disaster, the Deepwater Horizon oil spill.
The brown pelican is the smallest of the seven species of pelicans in the world. The only other indigenous North American species is the American white pelican, a common winter resident of Southwest Florida. The largest pelican in the world is the Australian pelican, which can weigh more than 22 pounds (10 kilograms).
The brown pelican is unique among these species in that it is the only one that dives for its prey. The brown pelican hovers from heights of 20 to 60 feet, then collapses its wings and plunges headfirst into the water, filling its pouch with a combination of minnows and saltwater. A fully extended pouch can hold almost three gallons of water. As the bird strains out the excess water, terns and gulls flock around hoping to pick off some of the outflow.
The brown pelican is especially vulnerable to water quality. Excessive nutrient runoff and the resulting harmful algae blooms can cause severe declines in minnow populations. With each pelican chick requiring 150 pounds (67 kilograms) of fish over the eight-month nesting period, an entire breeding season can be lost to environmental degradation. The brown pelican nests in large colonies, generally on remote and smaller uninhabited mangrove islands.
Predation occurs mostly to the eggs and nestlings from raccoons, opossums, bobcats, snakes, fish crows, and exotics such as Nile monitor lizards. Adults may be taken by sharks and alligators, though rarely. Coastal development, pollution, and pesticides are the pelican? primary threats.