Trade-offs between egg size and number in waterfowl: an interspecific testof the van Noordwijk and de Jong model

1. Van Noordwijk & de Jong proposed a model to predict the sign of an intra specific correlation between two life-history traits, given that a trade-of f between the two traits exists. In this paper, the model is adapted to egg size/number trade-offs. 2. The predictions of the model are tested within various clades of waterfo wl. Although the relationship between egg mass and clutch size in this grou p has been examined previously, prior analyses have either failed to take p hylogenetic structure into account or relied upon phylogenies that lack res olution. Phylogenetic structure is adjusted for using recently constructed phylogenies and the method of phylogenetically independent contrasts. 3. Van Noordwijk and de Jong's model was successful in explaining between-c lade variation in the relationship between egg mass and clutch size. Even i f a trade-off between egg size and number exists, a negative relationship w ill only be observed if the variation in the pattern of allocation (i.e. fe w large eggs vs many small eggs) is high relative to the variation in the a mount of resources invested in the clutch. Thus, this model may be useful f or understanding interspecific relationships as well as intraspecific patte rns.