Public information and conspecific nest parasitism in wood ducks: does nest density influence quality of information?

When nest fates are correlated among years, individuals may use information on the success of conspecifics (public information) to evaluate the relative quality of nest sites. In wood ducks, Aix sponsa, conspecific nest parasitism can reduce success at a nest site, especially at high nesting densities. Therefore, parasitism may influence the correlation of nest fates among years, as well as the quality and use of information. We examined the use of public information by wood ducks in four populations nesting in nestboxes placed at high (18-40 boxes/km) and low densities (5-9 boxes/km) along streams. Nest success was negatively related to density, but previous success did not consistently predict future success. Nests failed most frequently as a result of desertion, which was associated with nest parasitism. Nestbox use was higher for previously used boxes and at high-density sites. Clutch size, which we used as an index of parasitism, was higher in previously unsuccessful nests and was positively related to nestbox density. Thus, at high nestbox densities, nests that were abandoned, perhaps in response to parasitism, were also parasitized the following year and met with mixed success. Likewise, successful nest sites were not necessarily successful the following year. These findings might explain why wood ducks do not select nestboxes based on conspecific success. Contrary to results published for other cavity-nesting species, current success did not provide information about future success at sites with high densities of nestboxes.