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The number of birds of a flocking species likely to be ingested into an aircraft engine in a multiple birdstrike is of profound interest to engineers when they consider birdstrike tolerance in engine design. Of even more importance than the number of birds which may enter a single engine, when power can still be supplied by the remaining engines, is the probability of more than one engine suffering an ingestion. The historical birdstrike record can provide such information but is sometimes unreliable as it may be, of necessity, based upon unreliable data; the species of the birds involved may not be accurately identified and the number of birds ingested is often impossible to verify because of the nature of the remains (Allan and Hammershock, 1994). In addition, a historical record cannot reflect current or future trends in bird populations or behaviours. Some migratory populations of the Canada Goose (Branta canadensis) are thought to be in decline, but numbers are increasing in urban areas throughout Northern America and Europe (Allan et al, 1995, Seubert 1996, USDA, 1998). These introduced, non-migratory populations have adapted very well to man-made environments such as ornamental parks and reservoirs which are often near airports. In the absence of satisfactory control techniques becoming widely used, the probability of striking a Canada Goose will rise as its numbers increase. As it is a flock-forming species the risk of a multiple ingestion becomes particularly serious.