An experimental study of incubation effort in high-Arctic barnacle geese

1. We examined the cost of reproduction in high-Arctic barnacle geese (Branta leucopsis Bechstein) by manipulating the length of the incubation period by +/-5 days. Unmanipulated clutches were used as controls. 2. Nests with prolonged incubation suffered a higher egg loss to predators than control nests and nests with shortened incubation. 3. Among females with prolonged incubation, body condition at hatching was significant lower than among females with shortened incubation. These, however, did not increase their feeding effort to compensate for mass loss. 4. Increased levels of parental effort did not affect adult return rate or date of arrival to the breeding ground the following season. Accordingly, there is no evidence from this study that barnacle geese invest in young at the expense of their own survival or future fecundity. 5. We propose that breeding females retain some reserves at the end of laying in order to (i) incubate more continuously, thus shortening the incubation period and minimizing the risk of egg predation, and/or (ii) have a buffer against weight loss due to increased energy expenditure during inclement weather.