Body size, nutrient reserves and diet of Red-necked and Slavonian Grebes Podiceps grisegena and P. auritus on Lake IJsselmeer, The Netherlands

Samples of Red-necked and Slavonian Grebes that had drowned in gill nets while foraging in winter were analysed for body size, nutrient reserve levels and food content. Measurements of Slavonian Grebes indicated that they may originate from the Icelandic and Norwegian breeding grounds, not from the Baltic area as is suggested in the literature. The mass of the bird after its nutrient reserves have been totally depleted, its ‘structural size’, is best predicted by different body measurements in each of the 2 species and in the Great Crested Grebe, even though they are closely related. Total fat... Mehr ...