Do Predation Rates on Artificial Nests Accurately Reflect Predation Rates on Natural Bird Nests?

Artificial nests are widely used in avian field studies. However, it is unclear how well predation rates on artificial nests reflect predation rates on natural nests. Therefore, we compared survival rates of artificial nests (unused natural nests baited with House Sparrow eggs) with survival rates of active bird nests in the same habitat at the same sites. Survival rates of artificial nests (27.7%) were significantly lower than nest survival rates of natural nests (58.6%). Logistic regression analysis indicated that the inclusion of an index of nest concealment in addition to nest type (natural or artificial) significantly increased the amount of the variability in nest predation accounted for by the regression. However, because the relationship between nest survival and nest type (natural or artificial) was still highly significant even with nest concealment included in the model, we conclude that higher rates of nest predation on artificial nests were not entirely due to the greater conspicuousness of artificial nests. We suggest that lack of parental defense is an additional contributing factor responsible for higher predation rates on artificial nests and, therefore, is likely to be a potential confounding factor in future nest predation experiments using artificial nests.