Clutch size and nesting sites of the Mandarin DuckAix galericulata

The Mandarin Duck had a highly variable clutch size in both natural nest sites (tree cavities) and artificial sites (nest boxes); some very large clutches were recorded. The provision of artificial sites did not alter the size of clutches incubated in natural nest sites. However, the clutches incubated in artificial sites were smaller than those from natural sites when both were available. The addition of nest boxes to the study area substantially increased the total number of eggs incubated each year simply by the number of additional eggs incubated in boxes. Some nest sites, both natural and artificial, were unused in any one year. More than a quarter of clutches, both from natural and artificial nest sites, were never incubated; these were similar in size to clutches of incubated eggs. It is concluded that variability in clutch size resulted from intraspecific nest parasitism, and that the provision of artificial nest sites made little difference to the occurrence of this behaviour.