Incubation Rhythms and Mass Loss of Common Goldeneyes

Abstract

We examined simultaneously incubation rhythms and mass loss of 16 female Common Goldeneyes (Bucephala clangula). On average, female goldeneyes spent 81% of the day incubating eggs, and took 2.7 recesses per day, each lasting an average of 114 min. Females began incubation approximately 20% heavier than the lowest body mass they reached over the incubation period, a slightly greater mass loss than predicted for ducks their size. Goldeneye incubation behaviors were similar to those reported for other Mergini, and were consistent with the general relationship between body size and incubation behavior in waterfowl. Females differed in how they varied their incubation behavior in response to incubation patterns on the previous day and environmental factors, although females typically responded to warmer temperatures by spending more time off the nest. Female golden-eyes appeared to manage their mass loss by modifying their incubation behavior. Females tended to lose less mass on days following more substantial mass loss, and once females approached their minimum mass they spent more time off the nest. However, not all females were successful in this approach. Two females may have deserted their nests because they had relatively high mass loss (>20%) and reached a low body mass (about 600 g), and thus could not maintain incubation sufficient to hatch their eggs without putting themselves at further risk.