ENERGY METABOLIC-RATE IN BREEDING AVOCETS RECURVIROSTRA-AVOSETTA

We measured the field metabolic rates of six incubating Avocets by the doubly-labelled water method in a colony on the North-Frisian Wadden Sea coast in 1994. The Avocets had a mean field metabolic rate of 5.04 W (SD+/-0.33 W), which is only 2.3 times their basal metabolic rate a s calculated by the allometric equations of KERSTEN & PIERSMA 1987. Th e mean water contents of the Avocets was 66.8% (SD+/-2,4%). The water efflux was very high and showed a very high variation between the bird s (mean 178 ml/day, SD+/-48 ml). Avocets with a low body mass (females ) tended to have both higher water contents (in %) and higher water ef flux rates than Avocets with a high body mass (males); A comparison wi th other studies reveals, that the field metabolic rates of waders dur ing the breeding season are strongly influenced by the geographical po sition of their breeding sites and the related thermostatic costs.