Providing parental care entails variable mating opportunity costs for male Temminck’s stints

Males of many species theoretically face a fitness tradeoff between mating and parental effort, but quantification of this is rare. We estimated the magnitude of the mating opportunity cost paid by incubating male Temminck’s stints (Calidris temminckii), taking advantage of uniparental care provided by both sexes in this species. “Incubating males ” provide all care for an early clutch, limiting subsequent mating possibilities. “Non-incubating ” males include males that failed to obtain, lost to predation, or actively avoided incubating clutches. These males were free to pursue extra-pair copulations and to mate with females laying later clutches, which females usually incubate themselves. Male incubation classes did not differ in measures of quality, and many individuals changed classes between years, suggesting the use of conditional reproductive tactics. However, specialist non-incubators may also exist. Using microsatellites to assign parentage, we compare males’ total fertilizations and the subset “free of care ” fertilizations between incubation classes. Incubators were more likely to gain at least one fertilization per season, and averaged one more per season than non-incubators. However, successful non-incubators were more likely to gain “free of care ” fertilizations, averaging two more than successful incubators. The relative success of male incubation classes also changed with local sex ratios. With higher female proportions, non-incubators gained disproportionately more offspring, suggesting that the use of tactics should be partly determined by the availability of potentially incubating females. Overall, we estimate the opportunity cost of incubating at 0.13-0.25 of potential annua