Differences in depredation by small predators limit the use of plasticine and zebra finch eggs in artificial-nest studies

Small mammals. such as mice and voles. have been implicated as major egg pr edators of Neotropical migrant passerines by field studies using soft plast icine eggs or the very small eggs of Zebra Finch (Taeniopygia guttata). Nev ertheless, the effort required to depredate these commonly used egg surroga tes may be less than that required to depredate the larger, thicker-shelled eggs of most passerine species. To compare the depredation of these surrog ates to that of the eggs of a mid-sized passerine by a ubiquitous small pre dator, we exposed dissimilar pairs of plasticine, Zebra Finch, and House Sp arrow (Passer domesticus) eggs to captive white-footed mice (Peromyscus leu copus). Plasticine eggs were marked by mice more than either kind of real e gg, and Zebra Finch eggs were breached more often than House Sparrow eggs. We conclude that the use of either plasticine or Zebra Finch eggs may lead to overestimation of the ability or proclivity of small mammals to actually depredate the eggs of most passerines.