The relative importance of Australian magpies (Gymnorhina tibicen) as nest predators of rural birds in New Zealand

Abstract

Australian magpies (Gymnorhina tibicen) have been recorded as predators at nests of other birds in New Zealand but their importance as a predator in rural areas, where they are most common, has not been previously quantified. We continuously monitored 38 nests of seven species in rural areas over two successive breeding seasons using time‐lapse video recording to determine the proportion that were preyed on by magpies compared to other animals in this ecosystem. Twenty‐two lethal events were recorded over the two breeding seasons; magpies were responsible for only one of these. A further eight scavenging events were also recorded; magpies were not responsible for any of these. Harriers (Circus approximans), ship rats (Rattus rattus), and cats (Felis catus) were the main predators and were responsible for 36, 32, and 23% of lethal events respectively. A pukeko (Porphyrio porphyrio) was also recorded preying on nest contents on one occasion. Other known nest predators such as Norway rats (Rattus norvegicus), possums (Trichosurus vulpecula), hedgehogs (Erinaceus eu‐ropaeus) and ruru (Ninox novaeseelandiae) did not appear in any recorded frame although present in the study areas. Our results suggest that magpies are not serious nest predators in rural areas in comparison to ship rats, cats, and harriers, and that controlling magpies in rural areas will not significantly improve the nesting success of other birds. © The Royal Society of New Zealand 2006.