Premigratory Fattening in Knots: Food Conditions, Feeding Time and Intake Rates

摘要

The authors studied the food supply and feeding behavior of two subspecies ofKnot (Calidris canutus islandica and Calidris canutus canutus) during the (pre)migratory (re)fueling period in the Wadden Sea. Islandica was studied in March and April 1990 on Texel, The Netherlands, and canutus in May 1990 at Westerhever, Schleswig-Holstein, Germany. Faeces analyses showed that the diet of knots consisted of Hydrobia ulvae and Macoma balthica. The biomass equivalent of the droppings increased significantly in the course of the period on Texel. But since measurements on defaecation intervals are lacking, no conclusions about actual intake rates are drawn. Therefore the authors suggest that whether or not the knots manage to reach their optimal departure body mass, does not so much depend on increase in their energy intake, as well largely on the decreasing thermostatic expenses. (Copyright (c) 1993 Netherlands Institute for Sea Research.)