Can ground nesting birds escape predation by breeding in less productive habitats? A large-scale artificial nest study from Finnmark, Northern Norway

摘要

Predation is known to be one of the most important causes of nest failure in ground nesting birds, and many populations are experiencing a decline in breeding success worldwide. Predator abundance are expected to be highest closer to productive areas (i.e. Ecosystem exploitation hypothesis), and vary according to the availability of other prey (i.e. Alternative prey hypothesis). I hypothesized that ground-nesting birds can escape predation by breeding in less productive habitats, and that predation rates will vary according to small rodent abundances. To test these hypotheses artificial nests were deployed in nine study areas in Finnmark, northern Norway, over a four-year period along replicated distance-gradients from the forest border and into tundra plateaus (n=180*4 years). Predation rates varied annually according to small rodent abundances in support of the alternative prey hypothesis. Highest predation rates were found on nests placed furthest away from the forest border, and are therefore not in support of my productivity hypothesis. Ground nesting birds that breed on the tundra experience higher predation pressure than birds breeding in more productive habitats (e.g. forests), which might be a result of higher visibility of nests, and responses to the abundance of main prey or subsidies in nest predators.