Spotless crake: the wetland indicator

Department of Conservation —  22/08/2018 — 1 Comment

by Skye Wishart, Living Water Coordinator

The first time DOC ranger Rose Graham saw a spotless crake/pūweto (Porzana tabuensis), she’d been sitting for five minutes, motionless amongst the prickly beggar’s ticks at Lake Ruatuna, on an early February morning.

A spotless crake/pūweto. Photo: Gareth Rapley.

A spotless crake/pūweto. Photo: Gareth Rapley

From the listening station, the crake research team had played a variety of pūweto calls from a portable speaker – a long churrrrr, some wobbles and some clucks. A small movement in a gap in the vegetation caught her eye – a tiny creature, half the size of a blackbird. Its bright red eye shining out of its dark grey/brown plumage as it crept along on thin orange legs. Realizing there were no other pūweto at the source of the call, but rather three humans crouching in the mud, it raced away back into the dense lakeside undergrowth.

But from that moment Rose was hooked on this little-known and little-seen bird. Alongside Dr Emma Williams of Matuku Ecology, Rose is monitoring pūweto in Waikato’s Peat Lakes Rotomanuka, Ruatuna, and Areare where restoration work is being carried out by DOC and Fonterra’s partnership, Living Water.

Lake Ruatuna in the Waikato.

Lake Ruatuna in the Waikato

Why are pūweto so useful?

Ranger Rose Graham with a pūweto/spotless crake.

Ranger Rose Graham with a pūweto/spotless crake

Pūweto are a great indicator of the success of a wetland restoration, because populations can bounce back in just a few years with the right restoration conditions.

How? Pūweto can have large clutches of up to 5 eggs – sometimes twice per season – but nests and chicks are easy prey for predators. Pūweto also need specific plants and good water quality for habitat and food within their small home ranges. If thorough predator/weed control and restoration planting is carried out over a relatively small area – as long as it covers the pūweto’s home range – bird numbers should increase over just a few generations.

The three Waikato Peat Lakes in Living Water have had three years of monitoring thus far, and pūweto detected at listening stations (areas where pūweto calls are played) have increased from 11% to 42% of the time.

Living Water programme also shedding light on pūweto

The monitoring helps grow our knowledge of pūweto ecology and biology – they are so secretive and small, and their population so reduced with predators and habitat loss, that not much is known about them. In 2018, the movements of a radio-tagged pūweto showed it preferred the swamp reed raupō as habitat, and tracking over 26 days also shows how small their home range is.

The research has also shown that pūweto are one of the most difficult species to sex due to males and females having similar plumage. Few pūweto have been sexed by DNA to date that we don’t know what to look for. As a result, DNA samples from pūweto captured in 2017 and 2018 are also helping Massey University to figure out the best way to tell the sexes apart via their DNA.

A spotless crake/pūweto. Photo: Gareth Rapley.

A spotless crake/pūweto. Photo: Gareth Rapley

It is hoped further years of monitoring will teach us more about the wetland health and pūweto behaviour/biology.

A day in the life of: what it’s like to monitor crake?

To Rose, hours spent waiting quietly in hot sun or bitter rain, with arm outstretched holding up the radio antenna, are all worth it for the final result: the collection of data that gives us an indication of ecosystem health and a “drop more of knowledge we now have about pūweto,” Rose says.

With so little known about pūweto, everything is about innovation and experimentation. Here’s what the team gets up to:

Listening stations – whether working individually (Emma Williams) or in pairs (Rose and local Birds New Zealand member and Ōhaupō volunteer Kaye Turner) listeners sit for 10 minutes at each station, three times each summer, in the morning or early evening. Playing local pūweto calls intermittently, any sightings or sounds of the birds are recorded. In line with being such a shy bird, the pūweto were very rarely seen but sometimes up to three were detected.

Monitoring pūweto/spotless crake on a misty Waikato day.

Monitoring pūweto/spotless crake on a misty Waikato day

Trapping – or fishing? The team trialled catching pūweto using a Fyke net – a hinaki-type net usually suspended in water to catch fish. It has a series of funnel-shaped openings, which makes it hard for fish or birds to escape. However, on land the net must be properly suspended to utilise this design by using twisty ties, string, stakes and leaves, which has its challenges. Placed in a naturally occurring tunnel amongst the raupō, channelled with weed matting, the net caught two pūweto (one of which later escaped).

“Maybe next time we’ll get more if the equipment and matting stays in the environment longer – new objects can smell suspicious, maybe the matting smelt like Mitre 10 Mega to the pūweto,” says Rose. “There’s a whole world of trapping possibilities for trapping pūweto that we haven’t discovered”

Ranger Rose Graham with a pūweto/spotless crake.

Ranger Rose Graham with a pūweto/spotless crake

Tracking with a transmitter – with one bird wearing a tiny transmitter the size of a jellybean and weighing less than a gram, a team member tracked the bird every day for three hours in all weather, for 26 days. How? A hand-held radio antenna beeps the strongest when it’s pointed toward the transmitter-wearing bird. The tracker moves slowly and quietly towards the strong signal, taking care to avoid influencing the pūweto’s behaviour. Often the tracker will be within 10 – 15 meters of the bird, which usually stays out of sight in the dense lakeside vegetation. Every five minutes the tracker checks to see where the signal is coming from, and at what regularity, to know if the bird is active or inactive – for example, it might become inactive if it has stopped foraging and swapped places with its mate on the nest, or if the day becomes too hot.

“It would appear one of survival techniques of crake is that you can be right next to them and never know they are there. They can sneak across small open spaces without you seeing them at all,” says Rose.

A pūweto/spotless crake. Photo: DOC

A pūweto/spotless crake. Photo: DOC

This work wouldn’t have been possible without support from:

• The Living Water partnership (DOC-Fonterra) who funded Rose and Emma’s time, and the restoration work at the lake;

Awarai Kakariki (DOC’s national wetland restoration programme) who funded the resources required to trap and track the crakes;

• The Ōhaupō community volunteers for their predator control work and support with the bird counts, and

• Ngāti Apakura, local iwi for Lake Ruatuna – who gifted our pūweto Tx81 the name “Apakura” in recognition of their tupuna.

One response to Spotless crake: the wetland indicator

  1. 

    Thanks, this is one of the few useful articles on Spotless crake that I’ve read. Well done!

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