Ardea
Official journal of the Netherlands Ornithologists' Union

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Veldkamp R. (1995) Diet of Cormorant Phalacrocorax carbo sinensis at Wanneperveen, The Netherlands, with special reference to Bream Abramis brama. ARDEA 83 (1): 143-155
Recent diet studies in a Cormorant colony in NW Overijssel, The Netherlands, reveal that analysis of regurgitated stomach contents and pellets have several limitations. Nonetheless, the best results of year-round diet studies are to be expected from pellet analysis, especially if a correction for wear in the stomach is applied. Since pellet production of Cormorants rearing young seems to be irregular or even stops, pellets possibly do not give an accurate impression of food eaten by these birds. Regurgitated stomach contents collected during the breeding season are likely to provide a better idea of the food of Cormorants rearing young. Roach, Bream and Pikeperch are the most important prey species, as shown by analysis of both pellets and regurgitates. Total fish consumption of the colony in 1991 was estimated at 245 ton by pellet analysis. Cyprinids made up c. 74% of that amount. The mass share of cyprinids in regurgitates in April-July 1991 was 86%. It is shown that at the study area the consumption of relatively large Bream (up to 31 cm) is far more important than has been suggested by most studies elsewhere. Consumption figures derived from this study suggest that Cormorants at Wanneperveen consumed at least c. 5-16% on mass basis from the available standing stock of Bream in the lakes surrounding the colony in 1991, emphasising on the larger individuals ( gt 200 mm).


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