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 unc lear how well predation rates on artificial nests reflect predation rates o n natural nests. Therefore, we compared survival rates of artificial nests (unused natural nests baited with House Sparrow eggs) with survival rates o f active bird nests in the same habitat at the same sites. Survival rates o f artificial nests (27.7%) were significantly lower than nest survival rate s of natural nests (58.6%). Logistic regression analysis indicated that the inclusion of an index of nest concealment in addition to nest type (natura l or artificial) significantly increased the amount of the variability in n est predation accounted for by the regression. However, because the relatio nship between nest survival and nest type (natural or artificial) was still highly significant even with nest concealment included in the model, we co nclude that higher rates of nest predation on artificial nests were not ent irely due to the greater conspicuousness of artificial nests. We suggest th at lack of parental defense is an additional contributing factor responsibl e for higher predation rates on artificial nests and, therefore, is likely to be a potential confounding factor in future nest predation experiments u sing artificial nests.