The Forest Bridge Trust

Nikki Morgan, Marketing and Comms www.theforestbridgetrust.org.nz

Stoat monitoring

Wildlife monitoring cameras, also known as trail cameras, are increasingly being used by The Forest Bridge Trust (TFBT) as a tool to study and monitor mustelids (stoats, ferrets and weasels). The trust’s ecology and biodiversity advisor Virginia Moreno recently deployed 116 lured trail cameras across the rohe to learn more about the impact stoats are having on the ecosystem, and determine the effects that predator control and trapping efforts have had on stoat populations. Trapping catch data is measured on the TrapNZ App which gives us the number of stoats removed. We are now looking at measuring the abundance of stoats that have survived trapping. Stoats were introduced in the late 19th century to help reduce the rabbit population. They quickly established themselves as a significant predator of many native bird species, bats, lizards and invertebrates.

Stoats are clever and cunning creatures. They hunt day and night, moving quickly checking every burrow and hollow they come across, and will kill more than they need to eat. Ground-dwelling birds such as young kiwi, dotterel/tūturiwhatu and black-fronted terns/tarapiroe are easy targets. Stoats are particularly effective predators because they can kill kiwi chicks that weigh four or five times more than themselves. Birds that nest in tree hollows such as kākā and kākāriki are also vulnerable. According to Save the Kiwi, stoats are the main reason why 95% of kiwi hatched in the wild die before they reach breeding age.

To date, TFBT has mustelid control measures over 28,000 hectares, which is halfway to our goal of 54,000 hectares by June 2025. We had a great response from the community when we started to seek out landowners who might be happy to have trail cameras on their properties. Many property owners were already trapping on their land and are regularly recording their catch data via the TrapNZ App. We know from this data that for the last quarter of last year (Oct-Dec), 68 stoats were caught in the rohe.

Over the last month, we have been collecting data to obtain a cameratrap index (for example the number of stoats detected per camera per day) and occupancy (the percentage of cameras with stoat detections).

A total of 74 cameras are within mustelidtrapped areas and 42 in non-trapped areas, which will allow us to look at differences in relative abundance and occupancy between treatment and non-treatment areas. Cameras in non-trapped areas will provide baseline data so we can make comparisons after traps are introduced.

The results of the stoat monitoring project will better inform us of the effectiveness of our trapping efforts and whether we need to adapt trapping methods. It’s a long, ongoing battle but eventually, we hope that more and more people in the community will enjoy the benefits of fewer predators in the landscape and increased backyard bird song.

Info: www.theforestbridgetrust.org.nz

Shells and weather challenge wastewater contractors

More than 100,000 cubic metres of dirt has been shifted as work continues on the Warkworth to Snells Beach wastewater transfer pipeline project.

Watercare project manager Dirk Du Plessis says that due to the extreme weather at the start of the year, the work has been carried out in an intensified timeframe.

He says this was possible due to an impressive 90 tonne excavator.

“The launch pad at drive site two is now complete with a piling platform and a level stage for the separation plant,” Du Plessis says. “We are currently installing perimeter drainage and stabilising the headwall batter to prepare for the winter season.”

Meanwhile, environmental control work was temporarily stopped when some scattered shells were discovered.

“We immediately referred to the Accidental Discovery Protocol, contacted Ngāti Manuhiri and the project archaeologist who came out to the site and confirmed the shells were a previously unrecorded midden.

“The design of the sediment retention pond was subsequently amended and work re-commenced under the supervision and recommendations of the archaeologist and Heritage NZ.”

Du Plessis says the massive rain event at the end of January caused damage to the sediment ponds, which required some inventive remediation design to stabilise the batters of the ponds.

“We installed one-ton bags of gravel inside the ponds which allowed for the design capacity without increasing the footprint or encroaching on the identified archaeological zones.”

Meanwhile, contractors McConnell Dowell are now a year-and-a-half into the construction of the Warkworth pump station in Lucy Moore Park.

The circular emergency storage tank has been sunk to a depth of eight metres, alongside the previously sunk wet well/dry well. The project’s success in building adjacent underground structures using the caisson sinking method is a big accomplishment for the project team, and for McConnell Dowell, as it is a national first.

With the external casings for the wet well/ dry well and emergency tank in place, the next step was the internal fitouts which included three internal wall concrete pours. This was done in March. Attention is now on the civil works to excavate the deep pipe connections between the pump station and the emergency tank. In an effort to reduce waste, leftover concrete is being poured into formwork boxes made up on site to produce multiuse concrete anchor blocks.