Do different plasticine eggs in artificial ground nests influence nest survival?

摘要

In order to understand the role of plasticine eggs in nest predation studies, altogether 78 ground nests were monitored in a large wheat field near to Pécs (southern Hungary) in June 2006. Two eggs were placed in each of the artificial nests, comprising, in an alternating sequence, quail + quail, quail + natural colour plasticine, and quail + white lime coloured plasticine eggs. During one week 65.4% of the artificial nests were depredated. When the damage or disappearance of any of the eggs was considered as a predation event, the daily survival rates of nest containing only two quail eggs was higher than of nests with quail and natural plasticine eggs and significantly higher than of nests with quail and white coloured plasticine eggs. When considering predation to real eggs only, the results remained similar, however, the significant difference in survival rates of the two nest types with different plasticine eggs disappeared. Simultaneously with the nest predation experiments, 78 small mammal live traps were set up in the wheat field and operated for 7 nights. The capture success of traps baited with quail egg was 9.9%, with natural plasticine egg 15.4%, and with white coloured plasticine egg 23.1%, but only a marginal significant difference was found between daily survival rates of quail vs. white coloured plasticine eggs. Natural, but especially white coloured plasticine eggs resulted in an increased predation rate, therefore we suggest that in artificial ground nest experiments nest should be considered to be predated only when the real egg is damaged or disappeared.