Are adult nonbreeders prudent parents? The Kittiwake model

Understanding evolutionary consequences of intermittent breeding (nonbreedi ng in individuals that previously bred) requires investigation of the relat ionships between adult breeding state and two demographic parameters: survi val probability and subsequent breeding probability. One major difficulty r aised by comparing the demographic features of breeders and nonbreeders as estimated from capture-recapture data is that breeding state is often suspe cted to influence recapture or resighting probability. We used multistate c apture-recapture models to test the hypothesis of equal recapture probabili ties for breeding and nonbreeding Kittiwakes and found no evidence of an ef fect of breeding state on this parameter. The same method was used to test whether reproductive state affects survival probability. Nonbreeding indivi duals have lower survival rates than breeders. Moreover, nonbreeders have a higher probability of being nonbreeders the following year than do breeder s. State-specific survival rates and transition probabilities vary from yea r to year, but temporal variations of survival and transition probabilities of breeders and nonbreeders are in parallel (on a legit scale). These infe rences led us to conclude that nonbreeders tend to be lower quality individ uals. The effect of sex was also investigated: males and females do not dif fer with respect to survival probabilities when reproductive state is taken into account. Similarly, there is no effect of sex on transition probabili ties between reproductive states.