War on pests

The Department of Conservation’s Battle for our Birds was launched last year against the millions of rodents and stoats plaguing our beech forests and to protect the native birds, bats and giant land snails deemed most at risk. The programme included drops of 1080-laced cereal baits over about 600,000 hectares of conservation land between August 2014 and February this year. Here is a summary of the most recent report. 

DOC’s Battle for our Birds programme was launched last year in response to the biggest seeding or ‘mast’ seen in South Island beech forests for 15 years.  It’s aim was to protect native birds, bats and giant land snails deemed most at-risk from a seed-fuelled plague of rodents and stoats. 

When beech trees flower and then seed over summer and autumn native birds benefit from the abundant food.  But so do rodents, which build in numbers over winter, in turn feeding the stoats and priming their populations to explode the following summer.  The rats and stoats then prey on native species.

Without well-timed pest control, vulnerable populations of mōhua/yellowhead, kākāriki/parakeet, kiwi, whio/blue duck, kea, kākā, rock wren, native long and short-tailed bats, and giant land snails would have taken a serious hit from these predators.    

The impact of predator plagues had been seen before. Mōhua were wiped out at Mount Stokes in the Marlborough Sounds following the beech mast in 2000 and other populations of this small, yellow, hole-nesting bird were decimated in Canterbury, Otago, Southland and Fiordland.

The ramped-up pest control programme included the aerial speading of 1080-laced cereal baits over about 600,000 hectares of South Island conservation land in 27 separate operations between August last year and February this year to knock down rats and possums and kill stoats, which dine on poisoned carcasses.    

Use of on-the-ground methods such as poison bait stations and trapping networks were also stepped up.  More than a thousand new traps were put into the Murchisan Mountains in Fiordland to protect takahē from stoats.

Results from last year’s pest control show rat numbers crashing to undetectable or very low levels in many areas, providing a respite for native birds and bats as they bred over the summer.  However, with rodent and stoat results still to be analysed it’s too early to report on the overall success of the programme. 

DOC is also studying the effects of pest control on the target birds and bats.  The abundance and breeding success of species such as mōhua, whio, long-tailed bats, rock wren and kea will be monitored for two years after pest control.  Monitoring of long-tailed bats this summer in the Eglinton valley in Fiordland, for example, shows the population there remains healthy with a record number of some1700 bats counted from one roost. 

The longer term effects of repeated pest control on forest bird populations is also being measured in some areas. These results will provide more evidence of whether we are winning the battle for our birds.

See www.doc.govt.nz/battleforourbirds

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