Battle for our Birds: Newsletter 2, 2016

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Rock wren | Battle for our Birds

This is the second in a series of newsletters that will appear during the winter and spring of 2016 as the Battle for our Birds programme progresses.

It is very obvious in some places that in spite of winter, pest numbers have been sustained and are now climbing because of available food from abundant forest fruiting last summer. After monitoring pest populations we have worked out where the most benefit can be accrued for our native species. Rat numbers in some place are quite alarming and by the time you get this, the first few pest control operations may already have started. In other places, rats populations have not moved but the monitoring will tell us soon enough if there is an imminent threat.  

Download a printable version of this newsletter (PDF, 2,454K)


When the rat numbers climb, 
it’s time to take action!

DOC’s Battle for our Birds team met in late June 2016 to analyse the data from the hundreds of seed monitoring sites and thousands of rat tracking tunnels to identify where impacts of pest invasions would occur in the coming spring.

Data analysis showed a distinct pattern that has implications for where and when the response to rodent numbers will come. 

In some places, the levels of beech seeding will support rodent populations that will have a devastating impact if left unchallenged. Again, like 2014, the main areas affected are the northwest of the South Island in Kahurangi National Park.

Looking towards Mt Arthur, Cobb valley, Kahurangi National Park.

Looking towards Mt Arthur, Cobb valley, Kahurangi National Park.

Further south in the Otago mountains and to a limited extent into the eastern South Island, this pattern was repeated.

By mid-July more than 700,000 hectares were confirmed as ready to go with pest control and about 200,000 ha were on a watch list. Rat plagues look unlikely to threaten native species on a further 38,000 ha, which have been excluded.


In all areas of Kahurangi National Park, rodents are tracking at relatively high levels and the prediction of large rat numbers has prompted the need for pest control to tackle the threat to snails, bats and birds.

DOC has been working closely with longstanding community-driven conservation groups like ‘Friends of Flora’ and ‘Friends of Cobb’ who have put in the hard yards over many years to reduce the impact of pests on populations of native species.

The Friends groups have overseen the reintroduction of whio/blue duck into the area of the park where they undertake pest control. The ground-trapping operations keep the stoat and possum numbers in check during normal years.

Cobb valley, Kahurangi National Park

Cobb valley, Kahurangi National Park.

This year’s 1080 drop will control the expected rat plague, helping the native species survive and thrive in the years to come. Without rat control, all the hard work of the conservation groups may have been for nothing.

Some areas such as the Cobb valley are valued for the accessible hunting opportunities they provide.  

DOC has been working with the local branch of the New Zealand Deerstalkers Association to reduce the possible impact of aerial 1080 on the deer populations by including a deer repellent in the baits to minimise the impact on the deer population.

Mixed beech forest

Mixed beech forest

Silver beech Lophozonia menzesii

Silver beech Lophozonia menzesii.

Broadleaf seedling

Broadleaf seedling.

Counting the feet

The threat of rat plagues presents an opportunity to do some valuable research.

DOC has been quantifying exactly how many rats there are in a given area. Current measurements give us the extent of the threat but not an actual count.

We can extrapolate the current rat-tracking data to indicate what the threat level may look like in late August and November.

Rats have been tagged and released to monitor their actual movements and it will require close statistical analysis to get an accurate measure of rat densities.

So far, a 40% tracking rate means that there are about 8 rats per hectare. By the time we hit above 95% tracking rate (multiple rats tracking in multiple tracking tunnels) the density can exceed 20 rats per hectare.

Ross Mayley sets up a rodent tracking tunnel

Ross Mayley sets up a rodent tracking tunnel.

Ink pads are inserted into the tracking tunnel

Ink pads are inserted into the tracking tunnel.

Ink pads are inserted into the tracking tunnel
Bait is applied to tracking tunnels

Bait is applied to tracking tunnels.

Rat and mouse prints from a tracking tunnel survey.

Rat and mouse prints from a tracking tunnel survey.

Ecologists know that a 30% rat-tracking rate will be deadly for mohua – some sites already exceed this level.

And it’s not just rats. In some less ‘ratty’ places like the Waimakariri, mice benefit from the absence of rats and will form the basic food supply for stoats that will eventually threaten native species.

Aerial 1080 drops are not as effective on mice because of their relatively small range. In these places, where there is no ground control of stoats, there is an imminent threat to wildlife.

Already, rat numbers have exceeded expectations at Abbey Rocks on the West Coast, tracking at 74% in June.

Graph showing that rat numbers were tracked at 74% at Abbey Rocks in June.

2016 aerial pest control areas

Map of confirmed and proposed aerial pest control areas

This map shows confirmed operations (dark green) and proposed priority operations (orange).

Status of pest control operations

Check our website to see the status of pest control operations on public conservation land. We will continue to update this page as we receive more information.

Staff spotlight

Elaine Murphy: Predator ecologist

Elaine works for DOC in Christchurch but spends a lot of time at Lincoln University. She studies the ecology of stoats, rats and possums, and ways to control them.

Elaine is helping to develop new lures, deterrents and monitoring devices for stoats, rats and possums. Right now, stoats are in her sights as one of the biggest threats to New Zealand"s birds, reptiles and invertebrates.

Read Elaine's staff spotlight.

View videos showing Elaine's work with stoat lures.

Elaine Murphy at microscope

Elaine Murphy at microscope
Image: Tom Agnew 


Threatened Species Ambassador Nicola Toki introduces Battle for our Birds.

Nic Toki with kiwi

DOC scientist Graeme Elliot explains the more about the programme.

Video still: robin