Native bird abundance after Australian magpie (Gymnorhina tibicen) removal from localised areas of high resource availability

Abstract

Many reports exist of Australian magpies (Gymnorhina tibicen) attacking and sometimes killing other birds. One study concluded that magpies had little impact on the abundance of other birds at landscape scales, but another found that birds (mainly exotic species) avoided flying or landing close to them. We assessed whether continuously removing magpies for 6 weeks from localised areas of high resource availability (e.g. bush remnants or private gardens with fruit- or nectar-producing trees) in rural areas increased visitations by native birds compared with similar sites where magpies were not removed. Three count methods were used to estimate bird abundance: five-minute bird counts and ‘slow-walk’ transects in bush remnants, and five-minute bird counts and ‘snapshot’ counts in gardens. Generally, the abundance of native birds did not increase in treatment areas after magpie removal. In bush remnants, transect counts were typically better at detecting the presence of most species compared with five-minute bird counts. In gardens, snapshot counts were better at detecting tui (Prosthemadera novaeseelandiae) while five-minute bird counts were better at detecting magpies. Despite these differences, the different bird counting methods were generally in agreement and revealed that magpies had little impact on native birds at the scale we examined.