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  Environment » Natural Resources » Biodiversity » Native birds - Hamilton Halo » Report on the Hamilton Halo project – Five year review

Report on the Hamilton Halo project – Five year review

Hamilton Halo background

The Hamilton Halo project was developed by Waikato Regional Council’s Biosecurity-Heritage Group five years ago on the back of groundbreaking work by John Innes from Landcare Research.  Research by Innes and others at Landcare showed predation by rats was likely to be the largest single threat to the survival of tui eggs and chicks.  Added to the effect of other predators, like possums, the cumulative impact was that only 20-30 per cent of nests actually produced fledged birds. Innes identified controlling rats and possums to extremely low numbers during the September to January breeding season as critical to ensuring that more baby birds survived.

Five years ago, seeing a tui in Hamilton was extremely rare.  A few visited briefly in the winter, and then quickly disappeared.  Landcare research identified where these birds were breeding and how far they would fly to feed (approximately 20 kilometres).  The hypothesis was that if rats could be controlled in certain bush areas within that 20 km ‘halo’ then more birds would survive and eventually more would disperse to Hamilton where there was a large amount of exotic and (increasingly) native food available.

The technical difficulty involved in controlling rats to very low levels was considerable.  Comprehensive grids with a bait station every 75 metres were required and control had to be done just prior to the nesting season. Rat numbers were extremely high in some areas and large amounts of bait were consumed before the rat numbers fell dramatically.

In the early days of the Halo project, staff and the public needed to accept two unusual ideas:

  • First, that it did not matter what happened to rat numbers after the breeding season.  Rats are prolific breeders and numbers can climb quickly after control.  Nevertheless, while that has other negative ecological impacts, there is little direct danger to fledged birds. 
  • Second, that controlling pests 20 km away would actually mean more birds in Hamilton city. Many people wanted to see pest control undertaken in the city however, this would have protected only the common, introduced birds already here in large numbers.  

Lesson learnt after five years

Intensive control of rats is possible. It effectively protects native birds and for tui the dramatic results can been seen very quickly. The ecological results of the Halo project will be discussed in a subsequent section of this report.

The technical challenges of rat control have been mastered by council staff and contractors.  In fact, the price of Halo control work has dropped considerably from those first operations.

At a social and community level, Halo has been very different from other council pest control operations. The intentional and specific branding of Hamilton Halo has given it a power and profile that other pest control operations lack. Halo has its own Facebook page and has generated a level of public interest and involvement not matched by many other council programmes.

Partly, this is because Halo has been singularly outcome focused (more tui visiting Hamilton in a clearly defined time). This outcome focus is different from the council’s regular possum operations that stipulate residual trap catch (RTC) results but do not specify what measurable change there will be in the environment. 

The Halo project has benefitted from the large population concentration in Hamilton, which made it easier to energise and organise public involvement. Also, tui are a noisy, visible, charismatic species. Their recovery was always going to be noticed and celebrated.

Not all aspects of Hamilton Halo are easy to replicate in other areas and for other operations; nevertheless, we should try. The focus on outcomes is particularly valuable because it lets people know what they are getting for their money. It also creates community enthusiasm and momentum that can reduce the council’s own costs.  Several Halo projects have greatly benefitted from being partnered up with local community groups.

Community engagement and publicity
The power of the outcome focused branding of Hamilton Halo, along with the highly visible success indicator (more tui visiting the city) has seen unprecedented community buy-in, support and participation for this project. This has not just been limited to people living in the urban limits of Hamilton, but also in surrounding rural areas.


The Hamilton Halo Facebook page launched in 2009 continues to be very active and is the main way the community continues to engage with the council regarding the project. Three years from Halo’s launch into the social networking arena, the Halo Facebook page has 650+ fans following the site, and a general weekly total reach of between 300 – 500 people (that is the number of people who are ‘talking about’ the page including; ‘liking’ the page, commenting on or ‘sharing’ a post from the page, ‘mentioned’ the page in other areas of Facebook, ‘checked in’ on the page for recent updates.)

Fans post a wide array of information including tui sightings, photos, upcoming events fellow fans may be interested in, requests for advice, special moments that tui have created in their lives, educational opportunities. Those who post photos or commentary are encouraged to fill out the official ‘sighting form’ to help provide monitoring data of bird numbers/visits in and around the city.

Photo competition

In 2011, a photo competition was run as both a community engagement exercise, and to expand the bank of photos for Halo promotional material. The competition was very successful with around 50 photos received and the winning pictures being published in the Waikato Times and on the Hamilton Halo Facebook page.

Upcoming publicity/engagement

- A Halo stall at the Project Echo Bat Fun Day held on 10 March 2012.
- Interactive sessions in the Hamilton City Libraries July 2012 school holidays programme.
- A Halo case study in the new Enviroschools unit on biodiversity.
- An artwork/story-writing competition run in schools within the current Halo boundary.
- Updating the Project Halo brochure.

Halo results and future monitoring

Landcare Research Hamilton city biennial bird counts

One of the primary measures of success comes from the results of biennial city-wide bird survey conducted by Landcare Research in August and November every second year. The survey was initiated and funded by Hamilton City Council as an environmental sustainability indicator.

An excerpt from the most recent report states:
“One of the species to have increased significantly in August counts is tui, of which a total of 3 were recorded in 2004, 6 in 2006, 11 in 2008 and 38 in 2010. Assuming that individual birds are not counted at multiple stations, this 13-fold increase corresponds to a 3.0 per cent increase per year across all the count stations”

Although it is not known exactly how many of these tui are staying and breeding in the city, there have been numerous reports of fledglings and nest attempts.  Landcare Research scientists are confident tui are starting to nest in the city in small numbers. This has led to further discussion about beginning predator control in certain areas in the city.

Tui sighting reporting

In addition to the Landcare Research biennial bird count data, the council also monitors bird numbers via the Hamilton Halo website. An automated e-form allows members of the community to easily report a sighting on the webpage, from which we can tabulate total numbers of sightings throughout the year, as well as geospatially map where the sightings are occurring.

This summer (2011/12) we received more reported sightings of fledglings (which would indicate that tui have stayed in the city and gone on to nest and hatch young). Where possible we visit sites where fledglings have been sighted to confirm nests.

The table below shows the data collected via the council’s Hamilton Halo website from 2008 to 2012.  The first Halo operation was in 2007 and the table clearly shows the large increase in tui sightings two years later.  This concurs with what we know about tui breeding patterns, but undoubtedly also reflects the intense level of public interest/awareness. Note, the number of reported sightings decreases after 2009, while we know from Landcare data (and informal reports that do not get logged on the website) that the actual number of tui in the city continued to increase.

As we are reliant on the community for this information, we need to be mindful that over time the unsolicited public sightings will likely continue to decrease as tui become ‘the norm’ in Hamilton and the public stop regularly reporting sightings.  Now that the novelty of seeing a tui is wearing off, if we need to continue gathering this evidence for monitoring purposes, we may need to provide more motivation to have sighting forms completed.

Rat control

Halo sites receive three years of rat control and are then rested for two years. Contractors tender for the control work prior to nesting time and are required to get rat populations below a 5 per cent RTI (RTI – rat tracking index is the proportion of tunnels tracked in one night. For example if ten tunnels are set out and five had rat prints in them the RTI would be 50 per cent).

2011 rat tracking summary

Rat tracking tunnels are a permanent fixture at each Halo site. Tracking cards are placed in these tunnels for one night in the months of January, June and October. For example, Te Tapui A block, a 900ha rimu-tawa forest five kilometres west of Te Miro, tracked at 91per cent pre control and 1 per cent post control. The graph below shows that rat numbers climb quickly out of season, with the critical nesting period remaining low for three to four months after control.

Other sites controlled in 2011 were Tirohanga Road - tracked at 17 per cent pre control and zero per cent post control - and Pukemokemoke - tracked at 15 per cent pre control and zero per cent post control.

Future outcome monitoring

Now that it has been demonstrated rats can be controlled in certain bush areas and that more tui would survive and eventually more would disperse to Hamilton city, the question can be asked what wider biodiversity benefits are occurring within Halo sites? Possible future monitoring outcomes may be:

  • Healthy forest canopy is maintained when ‘Halo recipe’ implemented
    o Foliage cover 60 per cent+ or, flowering and fruiting or rata flowering
  • Weta population increases when ‘Halo recipe’ implemented
    o Tracking rates, weta hotel occupancy
  • Forest under-storey healthier when ‘Halo recipe’ implemented.
    o Canopy gap regeneration, palatable species, photo’s
  • Tui/bellbird/weta numbers increase when ‘Halo recipe’ implemented at key sites within the city.
    o Nest success/winter presence/weta motels

Future directions for Hamilton Halo

Landcare Research and the council have received several reliable reports of tui remaining in the city in December and January. This indicates the birds have moved from being just winter transients, to breeding here. It was always the intention of Hamilton Halo to begin limited pest control in the city when that happened. Discussions have begun with Landcare and Hamilton City Council to identify the most valuable areas to start controlling rats and possums during the birds’ breeding season. There will be challenges to doing pest control in urban areas but staff are confident they can be overcome.

Outside the city, the Hamilton halo is largely complete (with the notable exception of the Hakarimata Range) and into a regular control cycle. In Halo operations, possum and rat control is undertaken for three consecutive years, then the area is rested for two years.  This gives bird populations sufficient time to build up numbers. 

Staff are exploring how to apply the lessons learnt in Hamilton Halo to other areas, and in particular how to connect them with the Significant Natural Areas (SNA) project.  The committee will be aware staff are developing a programme to voluntarily engage with landowners who have SNAs on their property.  For example, a new SNA rates remission policy has been proposed in the draft LTP(external link).  The Halo concept of outcome-based, intensive rat and possum control could have a tremendous positive impact on biodiversity in some SNAs.

Staff believe Halo has greatly benefited from a clear geographic focus and would try to replicate that elsewhere.  For example, the results of the north west Waikato possum control schemes could be greatly improved if targeted Significant Natural Areas received Halo-like control.  Or a ‘Raglan Ring’ could be developed, building on the pest control and catchment improvement projects going on around Whaingaroa Harbour. The Whaingaroa catchment has numerous SNAs that would lend themselves to such a project. 

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