Pratt, H. M.

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Journal Article

Patterns of foraging trips of several species of colonially nesting birds have been examined recently for evidence that colonies serve as “information centres” to assist the members in finding food (Krebs 1974, Hoogland and Sherman 1976, Snapp 1976, Custer and Osborn 1978, Erwin 1978). According to this hypothesis colonial nesting is advantageous for species depending on food that is unevenly distributed and concentrated in areas of temporary abundance. Individuals who have difficulty finding food are able to follow their more successful neighbors to good feeding sites, thus reducing searching time and enhancing feeding success (Ward and Zahavi 1973).

Krebs (1974) found that Great Blue Herons (Ardea herodias) in a colony near Vancouver, British Columbia, tended to depart for intertidal feeding grounds in groups and birds from neighboring nests were likely to feed in the same areas on the same days. He suggested that less successful herons may have followed more successful individuals from the colony to areas of prey concentration. Although the statistical analysis of heron departures suggests that herons may follow each other on foraging trips, tracking individual birds as they leave the nest provides a more direct test of this hypothesis. This paper presents data on timing and directions of departures taken by breeding herons as they flew to feeding grounds from nests in a central California heronry. The results are analyzed for evidence of following and for information about the degree of colony dependence on the adjacent estuary for food.

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Pratt, H. M. 1980. Directions and timing of Great Blue Heron foraging flights from a California colony: implications for social facilitation of food finding. Wilson Bulletin 92: 489-496.