Dump Nesting in a Missouri Wood Duck Population

Dump nesting (2 or more hens laying eggs in 1 nest box) was a common phenomenon in a population of wood ducks (Aix sponsa) in southeastern Missouri. Nesting attempts increased from 47 in 1966 to 181 in 1974. Percentage of young from dump nests increased from 22 in 1966 to 86 in 1974. The additional production from dump nesting represented 23% of the young produced. Survival rates for young from normal and dump nests were similar. Dump nesting was not age related. Dump nesting females visited nest boxes before laying and some dumped eggs before nesting normally. Females tended to tolerate intrusion by other females during laying but repulsed intruders during incubation. Parasitic and host females derived maximum benefit from the limited nest sites available because of their behavioral characteristics.