The American white pelican is a large waterbird that lives across North America, breeding in the interior of the continent and spending its winters on the coasts. Unlike its relative the brown pelican, the American white pelican rarely plunge-dives for food. It typically swims on the surface of the water and grabs or scoops up fish and other prey with its pouch-shaped bill.
One strategy that these pelicans can use to increase their catch is cooperative feeding. In cooperative feeding behavior, groups of pelicans (usually less than 20) work together while swimming to herd small schooling fish into a dense ball or toward shallow water, where it’s difficult to escape. This behavior can start when the presence of pelicans attracts more pelicans to the area and a group forms. The pelicans then form a line or semicircle on one side of the schooling fish and begin to swim toward each other, closing in on the school. Once one pelican strikes at a fish in the dense school, the other birds immediately begin to strike, as well.
Some researchers have observed that smaller groups of pelicans (between two and six) are the most successful at catching prey using this cooperative herding behavior. The most effective group size likely depends on several factors, including prey density and whether too many birds increases the chance of a premature strike that could scare fish away.
To see American white pelicans feeding in a group, check out this video.Edit Summary
“When feeding with conspecifics, pelicans usually engaged in some form of “cooperative herding,” either driving fish into shallow water or surrounding them in more open areas. Members of groups of two to six birds caught significantly more fish than single birds or those in larger groups. Strike frequency initially increased with group size, reaching an upper asymptote at a flock size of four. Tests with decoys revealed that pelicans were attracted to areas by the presence of other pelicans.” (Anderson 1991:166)