Predation on artificial ground nests in relation to abundance of rodents in two types of forest habitats in the Tatra Mountains (southern Poland)

Abstract

Context The breeding success of ground-nesting birds is strongly related to the predation rate. Many predators feed primarily on rodents when the densities of rodents are high and change to alternative prey (eggs or young birds) when the main prey populations decrease. Aims During a 3-year study, predation on an artificial nest was related to population dynamics of small mammals in coniferous and deciduous forests in the Tatra Mountains (western Carpathians). Methods Small mammals were captured using the live traps. In deciduous forest habitats, we placed 36 traps and, in coniferous forest habitats, we placed 18 traps. In total, 174 artificial nests imitating broods of hazel grouse (Tetrastes bonansia) were located randomly in both types of forest habitat between 2012 and 2014. Predators of the artificial nests were identified by camera-traps at 87 nests. Key results Most of the artificial nests were lost to predation by mammals. The most numerous species of rodents in both types of forest habitat were the yellow-necked mouse (Apodemus flavicollis) and the bank vole (Myodes glareolus). A significant decrease in the number of rodents was followed by a considerable increase of predation on artificial nests. There were no significant differences in the rates of predation between the two forest-habitat types. Conclusions Our results support the alternative prey hypothesis and suggest that the breeding success of ground-nesting birds in the forests of the Tatra Mountains varies strongly from year to year, depending on the abundance of rodents. Implications Increasing of rodents’ density may result in lower predation pressure on eggs of ground-nesting birds. This finding may help modify recommendations for conservationists and forest managers to optimize their effort to save populations of Galliformes.