EFFECT OF INCUBATION BODY-MASS ON REPRODUCTIVE SUCCESS AND SURVIVAL OF 2 EUROPEAN DIVING DUCKS - A TEST OF THE NUTRIENT LIMITATION HYPOTHESIS

The nutrient limitation hypothesis postulates that variation in nutrie nt reserves during egg laying and incubation are important predictors of future reproductive success of female waterfowl. We tested one comp onent of this hypothesis in two European diving ducks, Common Pochard (Aythya ferina) and tufted Duck (Aythya fuligula), relating body masse s of incubating females to subsequent nest success, and to duckling an d adult survival. We based our analyses on 3,224 Common Pochards and 1 ,812 Tufted Ducks captured and weighed during the last two weeks befor e ducklings hatched at Engure Marsh, Latvia, in 1978-1993. Adult (ASY) females from successful nests weighed significantly more than those f rom abandoned nests, but differences in body masses between two catego ries of nest fates were negligible for yearlings (SY). For both specie s, survival (measured as apparent return rate) of females (SY + ASY) w as unrelated to their body masses. Duckling recruitment was independen t of adult female body mass for both species, but yearling Common Poch ards that provided recruits weighed more than those that produced none . Results of our study support the nutrient limitation hypothesis and we conclude that nutrient reserve levels may be important determinants of nest success in female ducks in general, especially for species th at rely heavily on endogenous reserves during incubation.