Flock formation in white pelicans pelecanus erythrorhynchos
O'malley J.B.E.; Evans, R.M.
Canadian Journal of Zoology 60(5): 1024-1031
ISSN/ISBN: 0008-4301 Accession: 005468004
White pelicans travel between breeding colonies and distant foraging sites in flocks. The process of flock formation during departures from colonies at East Shoal Lake, Manitoba [Canada] is described. Interdeparture intervals in 1978 and 1979 were significantly clumped, suggesting that individual white pelicans follow one another when initiating foraging trips. Flocks increased in size and made increasing use of air thermals as they traveled toward foraging areas. Flocks were most common and most variable in size between 1145 and 1345. Flock size was stable over the season, while the number commuting each day increased geometrically to a maximum by the end of the nestling period. Flocks observed near the colonies were characterized by low, horizontal, flap-gliding flight. Further enroute they flew higher and showed greater frequencies of gliding and ascending flight associated with increasing use of thermals. The results provide no support for the view that colonies and flocks represent manifestations of functional information centers. The results agree with the alternative interpretation that colonies and flocks facilitate group foraging and permit effective use of local enhancement as a means of locating thermals.