Research Diary

The analysis of the tawaki dive data we collected at Jackson Head and Milford Sound is largely in dry towels. And the results are pretty interesting.

The GPS data penguins brought home with them already highlighted tremendous differences in the foraging behaviour at both sites. The foraging ranges (that is, the distance the birds travelled during single foraging trips) differed by almost an order of a magnitude, with Jackson Head birds swimming up to 100 km away from their breeding colonies.

Foraging ranges of tawaki from Jackson Head and Milford Sound.

In comparison to other crested penguins this is not necessarily record breaking, but still was a lot further than any of the tawaki had travelled in the previous season. At the same time, the ranges of tawaki from Harrison Cove were unbelievably short. The average distance the birds put between themselves and their nest sites was a little above 3 km. Yes, not a typo – three kilometres. These are officially the shortest foraging ranges I have ever heard of in any penguin species!

So, how does that reflect in their diving behaviour and what does it mean?

https://vine.co/v/ip3FLI2hg6B

One could for example assume that penguins that travel a lot show a lower average dive depth compared to birds that hop in the water and start feeding straight away. Why? Well, when trying to cover distances it makes sense to move primarily horizontally which means many shallow dives.

And that’s what we found in the far travelling tawaki from Jackson Head. Almost half of the ca. 13,000 dives recorded in eight penguins were not deeper than 15 metres. The other 6,500 dives went down to depths of up to 90 m, although the majority ranged between 20 and 60m. So that is probably where the penguin were on the lookout for food.

So without having to travel at all… did the Harrison Cove tawaki dive deeper? No, quite the contrary! We recorded about 9,500 dives performed by six birds. And on almost 80% of these the birds stayed in the upper 15 m of the water column. What gives?

Depths of all tawaki dives recorded in 2015 at Jackson Head (orange) and Harrison Cove (green).

Well, underwater visibility in a fiord is quite limited. The fiord is usually covered by a freshwater layer created by heavy rainfalls that also wash a lot of detritus from the surrounding land into the water. As a result you don’t have to go down deep if you want to experience a night dive in broad daylight. This is also why in Milford Sound you can observe deep water species just a few meter below the surface.

For penguins as visually hunters that means that the darker it gets the less likely they are to spot their prey. So it seems to make sense for tawaki to stay up there… until you start to wonder why their prey does not bugger off into the darkness?

Well, perhaps it can’t because the prey the penguins were after was itself looking for food in the sunlit ranges of the fiord. Or the penguin food is brought passively to the surface by water movements. That applies for example to krill – which we found in considerable quantities washed up on the shore and which is a staple food for the tawaki’s closest living relative, the Snares penguin.

Occasionally penguin prey may be found at greater, darker depths. That may be the reason why almost all of the penguins occasionally dove down to 50 m or more. The record for the greatest depth stands at 80.6 m. After we lowered a GoPro into Harrison Cove, we can be sure that at such depths there is not a lot to see anymore.

https://vimeo.com/163773044

So what have we learnt?

We have learnt that the Harrison Cove penguins were a lot better off when compared to their Jackson Head counterparts. Not only did they not have to travel to some far away foraging grounds to find food. They also did not have to dive very deep to get to it. In short, foraging at Harrison Cove was pretty damn peachy.

Whereas at Jackson Head, life served the penguins lemons. And admire them for at least trying to make lemonade. The birds did everything they could to raise their chicks. And while it was unsuccessful for many of them, I am sure, next season will see the odds evened out between Jackson Head and Harrison Cove.

Last night word reached us that Inger Perkins from the West Coast Penguin Trust made a disturbing discovery while analysing footage from a trail camera deployed last season at Jackson Head.

Using motion triggered trail cameras the trust investigates the impact of terrestrial predators on tawaki at Jackson Head and Gorge River. We are closely collaborating with the trust and maintain the cameras while we’re in the field.

At Gorge River, trust cameras have already recorded how penguin chicks fall prey to stoats, which in New Zealand have wreaked havoc with all kinds of birdlife in the past century. At Jackson Head, however, it is mainly possums that tend to visit penguin nests apparently without causing them any grief.

And as such, analysing the video data has been an enjoyable affair that provided some neat insights into the family life of tawaki. That is, until Inger stumbled across said disturbing footage which raised the question whether Bigfoot or the Yeti might be roaming New Zealand’s West Coast:

https://vine.co/v/iwEhwtYiuJz

(Actually, it’s just a very cheerful Klemens Pütz triggering one of the cameras after checking on one of our GPS logger birds.)

The original shot used for the 2015 season field report cover

Although this season’s field work is long over – and, in fact, tawaki are currently going through their annual moult after a grueling and fantastic season (depending if you’re a penguin from Jackson Head or Harrison Cove, respectively) – we only now managed to compile or field report for the season. It can be found as PDF on our Download page and is easily reconginzed by the awesome and overwhelmingly green cover shot.

We have a good excuse for the late publication though. We have been busy with other penguin work on the Otago Peninsula where we trialled novel camera loggers on Yellow-eyed penguins. And despite a few organisational set-backs the trials went well and provided us with truly fantastic underwater footage of a penguin searching for and catching prey. Not strictly tawaki but too awesome not to share it here:

https://vimeo.com/149393078

We managed to deploy two more GPS dive loggers on chick-rearing female tawaki. The females are the sole providers of food for their chick while the male guards them. Last year, the females left early in the morning and returned in the afternoon or evening of the same day. In fact, they were very predictable that way.

This year, however, the birds seem to return at any time of the day. Data from the first logger deployments also suggest that the birds travel a lot further away from Jackson Head than last year.

A hard working female tawaki that travelled more than 200km to find food

The graph above shows the movement path and  dive profile of a 3.5 days foraging trip undertaken by a female tawaki. The bird covered at least 232 km in 85 hours 55 minutes. In order to cover such a great distance, the penguin could not perform a lot of deep dives.

The same foraging trip in 3D, although dives are difficult to see

The three dimensional representation of the female’s 3.5 day foraging track underlines the distances the penguins cover while searching for food. The red line indicates the corresponding section in the dive profile. Only when looking at the graph very closely, small wiggles are visible in the line. Those are the individual dives. Hard to see at this scale. But with all this travelling it is safe to say that the penguins are working incredibly hard this year.

Unfortunately, it doesn’t seem to be enough. We’ve received word that the situation is similar at other breeding sites on the West Coast. So we’re all a bit concerned what we will find next week when we relocate to Milford Sound.

We are enjoying gorgeous weather here on the West Coast while the rest of the country experiences pretty wet conditions. The weather certainly helped us getting three more data loggers on chick-rearing females last night.

A georgous sunset over Jackson Head.

Putting the devices on proved to be a rather quick job thanks to the fact that we are four people at the moment. In teams of two we could work simultaneously at two sites to start with. And having Klemens Pütz on board also turned out to be a bit of a game changer.

Klemens introduced us to a new technique to get penguins off their nests, which is as effective as it is simple. Klemens produced some catching hooks out of 3 mm fence wire he had found in Neils Beach. The contraptions look like primitive shepherd’s crooks – a length 2.5 m length of wire with the end twisted backwards to form a narrow hook. With the hook it is now possible to get penguins out of otherwise inaccessible burrows by gently pulling the birds out on one of their legs. It speeds up the whole process too so that logger deployments can be completed in under 10 minutes. That means a lot less stress for birds as well as researchers.

Klemens deploying the last logger of the night on a female tawaki

All three logger birds came from nests that seem to do rather well with healthy looking, reasonably fed chicks. Others were not so lucky. Another of our monitored nests failed yesterday where we found a freshly dead chick. When we later examined the stomach content of the small carcass we found a solid block of squid beaks occupying almost two thirds of the organ. Penguins cannot digest squid beaks easily and either need to break them down by swallowing small stones or just wait until they slowly dissolve. By the looks of it, being fed mainly squid is very bad for the chicks as the beaks quickly accumulate and cause severe constipation that eventually kills the chick.

Some of the chicks look quite skinny while others are doing better. On one of the three nests where we deployed loggers last night, the chick weighed 1.3Kg. The similar sized carcass we collected today was only 300g.

A male tawaki guards a rather skinny looking chick up at the Hilltop

Although it is rather sad to see so many nests fail, it is fortunate that we are here to study the penguins’ foraging behaviour. The data will be so valuable to see how El Niño affects these birds. Next year will surely be a lot better again – and so will be the foraging performance by the tawaki of Jackson Head.

We managed to get both data loggers back today.

The first bird did what we expected it do during the early chick-rearing phase, and stayed within a 8-km radius of Jackson Head. Unfortunately, she returned to a chick with dead nests as the male had abandonned his post in her absence. We did not know it at the time, but it was already an indication for what is happening here at the moment.

The second female performed two 2-day trips that took here 50km away from Jackson Head. Now, considering that she is caring for a very small chick that needs to be fed frequently, long-term trips are a bad idea.

Foraging tracks that illustrate the effort penguins have to put into feeding their young this season

Then again, we are observing a very bad breeding season for tawaki. While last season we counted two failed nests over the entire breeding season, we have already lost in the  8 nests in the week we are here. And it doesn’t seem to stop there. Chicks all over the place look rather small and do not seem to gain much weight.

It appears that the feeding situation out there is severely disrupted by El Niño. But it is really admirable how some dads hold the fort while mum is out trying her best to find food for their little ones.

A diligent das watching over its tired chick

Finally a break in the weather. Up until lunchtime we had fish swimming past the living room windows of our Neils Beach domicile. But within half an hour or so it all disappeared and made room for blue skies. And sunshine, actual real sunshine! Miracles do happen!

In the morning Ursula and Junishi drove down to Queenstown to pick up Klemens Pütz from the airport. Jun will be heading back to Dunedin. Klemens will take care of the Jackson Head tawaki tracking when we head over to Milford Sound in about two weeks.

We’re swamped down in Neils Beach. A heavy rainfall warning is in place for Westland with 130mm expected to fall until tonight. Not good news for us – and probably not good news for the penguins either.

Around midday a gap in the clouds opened up and the sun even peeped through it for a moment. But when it counted – in the evening – the rain returned with full force and reached almost biblical proportions.

Boring picture taken from our base at Neil’s Beach – nobody wants to be out in this kind of weather

Deploying data loggers in these conditions is really difficult. The adhesive side of the tape we use to attach the devices to the penguins will inevitably get wet and won’t stick that well. Once the tape is stuck to the devices it can withstand weeks in ocean water. But use damp tape during deployment and you have a recipe for disaster.

We called off today’s nest searches for obvious reasons. We will still try to get the first set of data loggers deployed on willing tawaki tonight. With breeding further advanced than we’d hoped, we haven’t got any time to waste.

https://youtu.be/J9Mr2FGK4zc

***

The weather wasn’t on our side this morning with heavy rainfall throughout most of the day. Nevertheless, we used a break in the weather to head out to Jackson Head after dinner tonight. Armed with three GPS logger/TDR packs we made our way along the coast to a site we call “Popi’s Plaza” (named after Popi Garcia-Borboroglu, president of the Global Penguin Society, who’s discovered it).

It’s densely vegetated with kiekie and bush lawyer, two plants that drive humans crazy because it’s so easy to get entangled in the former and ripped to shreds by the thorns of the latter. Once you have struggled through the nasty stuff, you’ll reach broadleaf forest where some tawaki breed in small caves and crevisses in a steep bank.

Scrambling over the rocky shore to our Jackson Head study site for the first time this season

First full day in the Jackson Head bush. As can be expected at the West Coast it turned out to be rather wet. And of course our timing walking in was impeccable at almost high tide, making clambering along the rocks a fun thing to do.

An image that defies the reality of the high tide that made walking kind of more fun

Once we reached the tawaki breeding sites we checked most of last season’s nests and observed quite a few changes. A bit of nest site shuffling seems to have occurred. Some nest sites remain empty this season, while new nests have been established in spots that had no users last year. Especially the apartment building, the site where most of the documentary filming happened last year, looked rather empty with a mere 4 nests where we had 9 last year.

An old fried is hodling the Fort at the apartment Building – the balcony bird is back!

Speaking of the apartment building. It was quite nice to see our old friend again, the male tawaki from the balcony nest. Last year he turned out to be a rather inquisitive chap ready to defend his chicks if somebody poked their nose to closely into the nest. Because of the nice natural lighting in the nest, he also became the star of the documentary.

The sleepy chick of the balcony nest

But overall nest numbers appear down compared with last year. The El Niño effect, perhaps? Also breeding seems more advanced when compared to last season. All nests we looked at had chicks in them, a few of them have already failed. In fact, in one nest I noticed a rather large chick by itself indicating that some birds have already gone into the post-guard stage.

Oh, and I spotted a penguin with quite a bit of its left flipper missing. We’ll call him Jamie Lannister. Just goes to show how tough these birds are and can indeed survive grueling injuries without human intervention.

The penguin equivalent of Jamie Lanister

After four hours of bush bashing we made it back to our base at Neils Beach. All pretty tired. The many weeks of desk work certainly take their toll. We hope to deploy the first dive loggers today. If only the weather improves a bit (no rain please).