Over prooien en prooiresten

It is pointed out that any food studies based on prey remains collected at elevated plucking posts are inherently biased. For instance, geese are too heavy to be transported by Peregrines. Among 6410 prey items amassed by Uttendorfer (1952) and his coworkers at 211 nest sites, not a single goose was reported. Similarly, there were no geese among 1365 prey items of Peregrines collected at a Dutch powerplant (van Dijk 2000); here, the Peregrine diet consisted largely of pigeons and Starlings. Uttendorfer listed six species of geese among prey remains found away from nests, presumably largely found in winter. However, plucks found in the field can lead to false conclusions as to the assumed cause of death and the predator responsible for the kill. Furthermore, Peregrines are known to feed on carrion and kleptoparasitise smaller raptor species. A less biased way of learning what wild Peregrines kill, is by direct observation of their hunting. Of 490 prey seen to be captured by Peregrines in Canada, 85% were waterbirds; the largest birds killed were female Mallards (Dekker 2009). An anecdotal observation is provided about an immature Peregrine hunting ducks. After much effort, a downed duck was pirated by a Herring Gull, which in turn lost the duck to a Bald Eagle. After a rest, the same falcon grabbed a gull over water. Unable to carry the catch to dry land, the falcon jettisoned its prey.