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Let a squadron of southbound pelicans but feel a lift of prairie breeze over Clandeboye and they sense at once that here is a landing in the geological past, a refuge from that most relentless of aggressors, the future. With queer antediluvian grunts they set wing, descending in majestic spirals to the welcoming wastes of a bygone age.
The American White Pelican occurs mainly in western and southern portions of North America, breeding inland in colonies on remote islands and wintering along warm southern coasts. The species is of particular interest because of its large body size, conspicuous white and black coloration, graceful flight, highly developed cooperative foraging, and the somewhat comic proportions of its large bill and pouch. White Pelicans are most commonly seen at foraging and adjacent loafing sites, where they are tolerant of human observers if not approached too closely. At breeding colonies, by contrast, they are shy and prone to desert or to leave eggs and young exposed to predators if approached.
Early spring migrants often arrive at colony sites before winter ice has left all surrounding waters. Courtship begins almost immediately, starting with aerial flights of often dozens of birds circling prospective breeding sites. Groups of newly paired birds at the same stage of the reproductive cycle then begin to form dense, synchronized nesting clusters or sub-colonies. As more birds arrive, additional sub-colonies form on other nearby portions of the colony, with the different sub-colonies commonly at different stages of the reproductive cycle.
Upon hatching, the altricial young are totally dependent on parents for food, warmth, and protection. By about 3 wks of age, they become more mobile, typically forming large overnight creches for protection and warmth, while the parents stay at the foraging grounds except for trips to the colony to feed their young. Generally only one of the two young survives, the other being harassed or killed by its older nestmate, a form of siblicide.
Favored foraging sites are shallow marshes, rivers, and lake edges, where mainly fish of little commercial value are taken. White pelicans obtain their food by dipping their bills into the water and scooping up prey. They do not plunge-dive from the air like Brown Pelicans. Like some of the Old World species of pelicans, White Pelicans are widely noted for their habit of cooperative foraging. Coordinated flocks of swimming birds encircle fish or drive them into the shallows where they become concentrated and can be more easily caught with synchronized bill dipping.
The continental population of White Pelicans was considered threatened until the early 1960s by combinations of changing water levels, human disturbance, and possibly contaminants. The population has since recovered and continues to increase at >3%/year. These increases have created conflicts with the aquaculture industry in the Southeastern United States in the last decade, especially during spring migration.
The first significant inquiry into the biology of the American White Pelican was a study of food habits relative to game fish interests by Hall(1925) at Pyramid Lake, Nevada. Thompson (1933) provided the initial estimate of the continental population, which has been repeated at various intervals since (Sloan 1979, Vermeer 1970, Sidle et al 1985). Behle (1958) summarized a decade of studies of the natural history of the species on Great Salt Lake, and that volume along with the ethological observations of Schaller (1964) stimulated many additional studies of behavior and physiological ecology by Evans and his students at the University of Manitoba and breeding biology ecology by Knopf at Utah State University. Recent studies by King and his associates (King and Michot 2002, King and Werner 2001) have again focused on behavior and food habits of the species, specifically relative to economic impacts on aquaculture in the Mississippi River Delta region.