Counterintuitive parental investment by female dabbling ducks in response to variable habitat quality

A central tenet of parental investment theory is that parents should invest more in offspring that are more valuable. Among prairie waterfowl, ducklin g survival is higher in wetter years. Thus, we tested the prediction that f emale dabbling ducks should take greater risks protecting their offspring i n wetter years. As our measure of risk-taking, we used the distance at whic h incubating females flushed from nests when approached by an observer. Dat a were collected for Mallard (Anas platyrhynchos), Blue-winged Teal (A. dis cors), and Gadwall (A. strepera) nesting on the same study area in south-ce ntral Saskatchewan, Canada, over a 14-yr period during which wetland abunda nce varied by almost an order of magnitude. Flushing distances of incubatin g females varied significantly with wetland conditions in all three species , but in a direction opposite to that predicted. Female ducks risked less f or their nests in wetter years. These results could not be explained by dif ferences among years in nest initiation dates, renesting potential, clutch size, or age structure of the breeding population. We propose that our coun terintuitive results may be a consequence of the way in which wetland abund ance affects the cost of reproduction in these ducks. If postbreeding survi val of females is higher in wetter years, and increases faster than that of their ducklings as a function of increasing wetland abundance, then the Va lue of the females to themselves (i.e., future reproduction), relative to t he value of their current reproductive attempt, could favor reduced parenta l investment in wetter years.