Rabbit Abundance Influences Predation on Bird Nests in Mediterranean Olive Orchards

Abstract

In recent decades, the intensification of agricultural practices in olive orchards, including intensive use of agrochemicals, along with the absence of natural herb layer, has led to a decline in songbird communities. Increased nest predation has been suggested as another important factor in the decline of farmland birds. High abundances of alternative prey species, such as European Rabbits Oryctolagus cuniculus may attract generalist predators, which may increase predation rates on bird nests, a phenomenon known as hyperpredation. In this work, we evaluate artificial nest predation in intensively farmed olive orchards, using quail eggs (one plaster and two natural eggs in each nest) placed on the ground (97 nests) and on trees (106 nests). 53.7% of nests (109 out of 203) were predated; 51 of these nests had at least one egg with signs of predation and in 58 nests all eggs were predated. Nests placed on the ground (61%) were predated more frequently than those on trees (46%). Rabbit abundance was identified as one of the main factors increasing the probabilities of a nest being predated. Despite lower rates of nest predation in areas with low rabbit abundance, we found a higher diversity of nest predators, such as Mustela nivalis, Mustela putorius, Martes foina or Erinaceus europaeus in these areas. This study suggests that conservation efforts aimed at increasing the breeding success of farmland birds should avoid areas with high abundance of rabbits owing to the phenomenon of hyperpredation.