Scientists Confirm Magpies Bad for Native Birds

Forest and Bird, Issue 302, 1 November 2001, Page 6

Scientists Confirm Magpies Bad for Native Birds

DIANA LEUFKENS

ontrolling magpie ‘\-/ numbers may help build up populations of native birds, particularly tui and kereru, according to preliminary results from a major scientific trial. Landcare Research is coordinating a four-year study examining the effects of magpies on other birds in rural areas. The fieldwork is being undertaken by regional councils in five areas: Northland/Auckland; Waikato; Bay of Plenty; Wellington and Southland. Each region has two study blocks covering several hundred hectares: one where magpies are killed, and another where they are not. All types of birds were counted in all blocks in late 1999 before magpie control started, then again in late 2000 after several months of magpie control.

Preliminary analyses of bird counts show that numbers of native pigeon, and three introduced birds (blackbird, skylark and song thrush), increased in nearly all blocks when magpies were killed. Tui, mynahs and spur-wing plovers also increased in most of these blocks, although more data is required to confidently attribute those increases to magpie control. Landcare Research pestecologist John Innes says the results are based on bird counts after just one year of magpie control. Two further annual counts are planned. ‘If the increases noted so far are real ecological effects, due to fewer magpies, then even bigger differences between the ‘kill blocks and the ‘non-kill’ blocks should emerge. ‘The interim results should

not yet be taken as a scientific mandate for destroying magpies, but they do suggest that some benefits of magpie control are likely, John Innes says. ‘There is anecdotal evidence from landowners that kereru (New Zealand pigeon) are seen more often after magpie control, and so far the research confirms that. "Magpies occasionally harass any bird flying or feeding in the open in the magpies’ territory. In the cases of tui and kereru at least, this seems to be independent of the diet of the persecuted birds since magpies eat mainly pasture insects, while tui and kereru eat nectar, fruits and foliage. Mr Innes says up to 1200

magpies were removed from each of the kill blocks, and the large numbers were a surprise. ‘Council workers found up to 20 times more magpies than they thought were present, he

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