Breeding and Natal Dispersal of the Goldeneye, Bucephala clangula

SUMMARY (1) Breeding and natal dispersal were examined for female goldeneye breeding in nest boxes in Sweden. Females changing nest box between years dispersed a median distance of 0 75 km to the new nest box (or, to the tenth nearest nest box). Individuals (N = 17) which returned to the natal area to breed, nested in the vicinity (median = 0 73 km) of the box in which they had hatched. (2) Neither the proportion of females changing nest box, nor the distances moved between nest boxes, varied among years. (3) Forty-two percent of females reoccupied the same nest box in successive years. Females which failed to breed successfully were less likely to return to the same nest box than females which bred successfully. (4) Females which moved to another nest box were less likely to hatch their broods successfully than females which returned to the same nest box. When they moved they produced smaller clutches and broods, and bred later in the season than when they returned to the same nest box. (5) Among females which moved, those which had failed to breed successfully moved further to another nest box than those which had bred successfully. In the case of females which lost clutches to predators, moving away from the vicinity of the previous nest box may have been advantageous, since boxes in which clutches were preyed-upon tended to be preyed-upon in the following year and also tended to occur close together. (6) The greater the distance from the previous nest box at which females bred, the less likely they were to start egglaying early in the season. (7) Females whose previous nest box was occupied by another female moved further to new nest boxes than females whose previous nest box was left empty.