Tasman Every Day

This photo of the Milky Way was taken at Upper Moutere. Back in the early 1960s, the University of Pennsylvania surveyed several sites in the South Island to see if they were suitable for establishing an observatory. Away from the main towns, the Tasman District has very little in the way of light pollution, and Mount Malita (960 m) in the Mount Richmond Forest Park was a candidate before Mount John (1029 m), near Lake Tekapo, was finally selected. Eventually the American university partnered with the University of Canterbury in establishing the Mount John Observatory, and a dark-sky preserve was established around the observatory in 2012. The reason the Mount Malita site was rejected? Too much rain. While the Tasman District is certainly wetter than the Mackenzie country, there are still plenty of clear, dark nights that make it possible to enjoy the glories of the southern hemisphere’s skies.

This is a Pelton wheel, the type of water turbine used in the Cobb Power Station. The Pelton wheel is suited for hydro stations that have a high head, which Cobb does. They are very efficient and can generate power from a small volume of water. For instance, the flow of the Cobb River into the reservoir is roughly equivalent to the flow of the Avon River through Christchurch city, and, let’s face it, the Avon is kind of just a big stream. Because there’s such a drop from the reservoir down to the station with the Cobb, a large amount of pressure is built up by the head. This pressure is then focused into nozzles that raise the pressure even higher. The result is that a very small amount of water spurts out the nozzles at high speed into the cups of the Pelton wheel. This spins the wheel to incredibly high velocities and all this energy is converted into power. Most other hydro stations in New Zealand don’t have such a high head; instead of Pelton wheels, they use Francis turbines that rotate at much lower speeds and require much higher volumes of water to generate power.

The Cobb Valley track runs alongside the Cobb River, and this is the view in the lower part of the valley, walking out towards the Trilobite Hut carpark. The valley floor is covered in tussock, these knee-height grasses growing in clumps that you can see in the foreground. From a distance, tussock give the landscape a nubbly appearance, kind of like how a polar fleece pills when it’s getting a bit worn out. The name “tussock” refers to the clumping nature of the grass. The stems of a tussock are tightly packed together and this helps the plant to collect and retain water, including water from fog. Because of this ability, they do well in dry environments and are common throughout the South Island’s mountains, painting the mountains a tawny gold.

Yesterday’s photo was of two weka (Gallirallus australis) chasing each other and is a blur of feathers where it’s a bit difficult to tell which end of the birds we’re looking at. Today’s is a proper photo of a weka close-up. The subspecies of weka that is found in the Tasman District is the western weka, Gallirallus australis australis, and it’s doing better than other subspecies. These guys are characters, and if you’re camping near them, you need to keep your stuff secure, because they will steal it. It doesn’t even have to be food or shiny for them to take their chances. Once I was camping with friends whose year-old daughter needed her nappy changed. Mum folded up the dirty nappy and put it to one side to be disposed of once the fresh nappy was in place. A weka darted in and snatched the dirty nappy, taking off across the campground. The nappy was too heavy for it, so it didn’t get far.

Okay, this isn’t a great photo, but it illustrates something I find really amusing about weka (Gallirallus australis). Weka don’t mind you getting near them, what they won’t tolerate is others of their kind getting close. If another starts closing in, one will start clucking, slowly at first, and becoming increasingly insistent as the intruder bird gets closer. If intruder bird doesn’t Back! Off! defender bird will chase it, in which case both will forget about you entirely while intruder bird runs in a zig zag trying to stay well ahead of defender bird, and one or both of them raise their wings. Trying to look bigger? Or maybe fly? As with quite a few of New Zealand’s native birds, weka don’t fly. They hang out in groups near human habitation—in this case a hut in the Kahurangi National Park—barely tolerating each other. In spite of their intolerance of each other, they are not a threatened species, so it seems their intolerance doesn’t last into the breeding season. Male and female weka share in the incubation of the eggs and care of the chicks.

This is the view from the eastern slopes of Xenicus Peak looking down on Lake Cobb. This tiny lake is the source of the Cobb River, which flows into the Cobb Reservoir, providing water to the Cobb power station at the junction of the Cobb River and the Takaka River. Who was this Cobb who gave his name to so many features in this part of the Kahurangi National Park? The only information I could find is that he was a prospector. The region hosted a small gold rush in the 1850s, and that is, it seems, where the name “Golden Bay” comes from, so not from the golden sand beaches. Up here around Xenicus Peak, it’s beautiful, wild country, rocky outcrops with tussock and other low-growing sub-alpine plants giving way to the beech forest that surrounds the lake. There’s a rainbow in this photo, it’s a little bit hard to see, but it runs across the top end of Lake Cobb, through the trees surrounding it.

This imposing beast is Xenicus Peak in the Cobb Valley. Xenicus is a genus of very small birds, containing only two species. The first is the New Zealand rock wren (Xenicus gilviventris), which is now extremely rare. It occurs in a lot of different parts of the South Island, but there aren’t very many of them. In 2008, the Department of Conservation started transferring rock wrens to a rodent-free island in Fiordland, where they have been able to breed. The second Xenicus species is (was) the bush wren (Xenicus longipes), which was common throughout the country when Europeans first arrived. Rats took a toll on the population, but it was stoats, introduced in 1884 to control rabbits, that really pushed them to the point of extinction. Bush wrens were last sighted in the South Island in 1968, in Nelson Lakes National Park. The Stewart Island subspecies was doing okay until the 1950s, when feral cats started penetrating the island’s more remote parts. In the early 1970s, six birds from the Stewart Island subspecies were moved to Kaimohu Island, which is part of the Snares group southeast of Stewart Island. They didn’t survive, and the species has been regarded as extinct since 1972.

The colours of the welcome swallow (Hirundo neoxena) are striking and distinctive; there are no other birds even remotely similar in appearance found in New Zealand. They’re fast, though, so you’re more likely to see them in flight, swooping under and over bridges or around the eaves of buildings. The swallow’s rust-coloured face and throat gives way to a navy cape flowing down its back to its forked tail, topped off with black eye stripes that make the swallow look a bit like an elegantly masked bandit. The only thing they steal is insects snatched from the air. They are sometimes regarded as pests due to their habit of building nests on human structures, which can turn into a noisy mess once the chicks have hatched. Swallows choose vertical or near-vertical surfaces out of direct sunlight for nesting sites, and bridges, houses and outbuildings provide plenty of such surfaces. Swallows build their nests from mud with a bit of grass mixed in. It takes them from one to three weeks to build and nest, and nests are often reused from year to year.

This photo was taken in 2014 and shows the view from the Cobb Power Station back along the Cobb Valley Road. You can see how narrow and windy the road is, not to mention the steepness of the hill rising above the road. Cyclone Gita damaged the area pretty badly earlier this year, so it will be interesting to get up there later in the year and see how it’s changed. That’s the Takaka River flowing alongside the road. The Takaka River contributes to waters of Te Waikoropūpū Springs through seepage into the Arthur Marble Aquifer. Pupu Springs is one of the clearest bodies of water in the world. Water can take as long as ten years to get from the Takaka hills through the aquifer to the springs.