South Island Robin

We moved 29 South Island robin from nearby Te Kakaho back in March and August 2013, so why so long to write it up? Laziness for sure, and reticence, lest the translocation dwindle away to a failure over time.

Island-bred robin, 2016. For a video record of nesting from hatching to fledging, please see: https://www.youtube.com/watch?v=HuiFuYydWOk

Right from the beginning of this project we thought robin would be an obvious candidate for reintroduction. They would certainly have been present before the arrival of rats in the 1800s. Peter proposed that Tinui of all the Rangitoto group of islands might be the best place to let them go as it had more forest cover than Puangiangi or Wakaterepapanui. A rep for the Tinui owners reckoned we should go with Puangiangi and presciently observed that they would end up on Tinui also in fairly short order anyway.

The project was endorsed by Ngati Kuia and Ngati Koata as gifting and recipient iwi respectively, and most of the birds were caught in August 2013 by Peter, Willie Cook, Ruby Collier, Bill Cash and Katrina Hale. Ros Batcheler who caught in March (which was mostly about kakariki rather than robin) was on hand to meet the birds, the big Ngati Koata welcome led by (the late) Joe Paul having been completed in March. Most birds were released centrally while Peter and Ruby had a quick trip down to the south to release three pairs in a piece of forest we have since dubbed Robin Bush. Free boat transport for birds and people was provided by (the late) Danny Boulton.

Courtship feeding was likely observed during the week after release, and three nests and two fledged young were seen only two months after the bigger release. A reasonable number of the original 29 have been seen over the years but we can’t really say what percentage of them formed the founder population given the difficulty in surveying all likely habitat. Two of the founders were still around in winter 2021 and it has always been a pleasure to see an old friend (minus the odd colour band) come up close to see if we are edible or will find some food for them. One of these founders is most often seen when we are weeding an area near Robin Bush, on a steep slope with very tight vegetation. It’s nice to see the elderly banded robin pop up in your little bubble when you are surrounded by a dense, scratchy botanical garden with visibility of only a couple of meters in any direction. Robin certainly add to people’s enjoyment of the island- if you don’t already know, they are confiding and aggressive. They think nothing of jumping on to your boots and picking at the laces, and I have had to shoo one off of my head repeatedly as it attempted to harvest any remaining hairs. They like to collect bugs from a scrape made with a boot, but they put paid to a favourite party trick of showing guests the pile of geckos sheltering between old sheets of corrugated iron when one quickly showed up and started scoffing the smaller geckos.

Numbers increased very strongly in the southern third of the island, but with very few being seen in the northern third until recently. In the central third around the house and nearby forest and shrublands, numbers initially built up quite well, yet we then appeared to witness two cycles of local extinction and recolonisation there. This aspect of the reintroduction made me the most nervous. Did the arguably more open forest structure allow falcon to take them under the canopy? Was there something toxic in the old rubbish dump (which we have cleaned up as best we can)? Did the larger population of kereru there compared with the rest of the island lead to disease transmission through the water supply (I did see an apparently OK robin go on to expire by the water trough a mere 15 minutes after I first saw it)? Or were we just seeing what happens in slightly less favourable habitat when food runs low seasonally? On the last point, Lynn Adams has noted on Mana over the other side of the Strait, that robin numbers go through frequent peaks and troughs, with good breeding yet apparently low survival beyond a season or so. The most obvious explanation would be that the less well established forest on Mana lacks enough food say in a dry autumn. In Wellington harbour, translocation of robin to Matiu Somes failed over a few seasons, despite breeding being observed. If there was a problem on Puangiangi it seems to have fixed itself and over the last couple of years robin have again become very common in the central area.

As of now, robin are common in the established forests and abundant in the regenerating shrublands of the southerly two-thirds. They have even colonised the heavier tauhinu scattered in the rank pasture, and are moving north, where they are now commonly seen.

Robin are probably at carrying capacity over a good part of Puangiangi. Bill Cash, who was the main force behind bird reintroductions to the almost identically-sized Motuara in Queen Charlotte Sound, estimated the robin population there at 300-600. We might be looking at a similar number on Puangiangi fairly soon. They could also easily be seen on Tinui by autumn 2016 (Colin Miskelly has documented several other examples of robin colonising islands by making sometimes quite long flights over open water; the distance to Tinui was probably not a particular challenge). A single bird was also seen on Wakaterepapanui to the north in spring 2021. I think it’s time to call Success on this one.

Sooty Shearwater- We Still Have No Idea

 

2020 Sooty shearwater chick a couple of days before fledging, doing wing exercises. Burrow is at bottom right.

Readers will know that the main sooty shearwater colony is very up-and-down in its productivity. In 2019 for example, we think only one chick fledged despite the usual active start to nesting. 2020 was much better, with 18 occupied burrows in January and 14 in March. We lost the last two months of burrowscope monitoring after that because we stayed away during the various levels of Covid lockdown, but we haven’t previously had big losses after February and presume all or most of the 14 burrows active in March  fledged chicks this year.

In an earlier poor season we had asked Graeme Taylor what he thought was going on, and he reckoned that productivity had been average around the rest of the country, and that we should look to problems on site. This season we asked Henrik Moller to think about what we were doing and to see if we could influence anything. Henrik suggested firstly that we look more widely for evidence of colony expansion than just the monitored burrows, as obviously this would be the desired outcome rather than just monitoring burrows for monitoring’s sake. We were aware of that but his comments helped overcome the ever-present activation barrier to searching the less-than-level terrain. Over the entire accessible forest floor we found one new burrow, which we decided not to include in the monitored group given the likelihood of taking a decent slide downhill while getting to it. To be certain, I tested this likelihood and confirm that gravity does indeed work on site. We also decided there was little to be gained by actively monitoring the northern outlying burrows discovered by Jo Sim and Rua. In particular, the larger of the two known areas is quite unstable and we are likely to collapse burrows if we go there often.

Henrik Moller also said that sites he has been involved with can have a proportion of false negatives, when the burrow appears empty but the chick merely moves deeper away from the probing burrowscope and can’t be seen in time. We don’t think this is a massive problem with our colony, as the burrows are not highly convoluted and interlinked like some well-established sites. However, the video at the top is from a false negative burrow. It was obvious a chick was present (swept entrance, excreta, smell: so we put the camera on it) but it did come up empty in the burrowscope inspection. Now that I in particular am more aware of false negatives, I’ll be making special effort to avoid unconscious bias in effort and attention when looking at a burrow that measured empty the previous month.

Given the disrupted monitoring season, we don’t know if falcon or weka got any chicks this year, but the trail camera showed half a dozen single-weka visits to the burrow in the video above. These were by way of a passing inspection, and the weka did not attempt to enter the burrow as far as we know. We seem to have weka at very low levels now, and indeed we heard only a single bird over the entire island this June with the previous two visits turning up nothing.

This is also a good opportunity to back away somewhat from a claim I made in 2013, that the speaker system by the colony was responsible for the birds coming back after a long absence. The basis for this was that the colony looked seriously deserted in May 2012, yet for the 2012-3 season after the speakers went in there was plenty of activity and obvious cleared areas throughout, which were not there on our initial visit. If 2011-12 had been a no-fledge season though, then the colony might just have looked sufficiently forlorn in May 2012 for us to pronounce it extinct at that time. We still think the speakers did work, but must allow for the possibility that we were fooled. We’ll never know.

So, what’s going on then? Our best guess remains that the colony is just like Titi Island  nearby, which has been static or shown only very slow growth over the last 20-30 years. The Cook Strait area is not rich in sooties and may be a bit far from the southern feeding grounds, so inexperienced breeders (like we allege ours to be) may not be invested enough to carry on with chick feeding if the krill moves further south in a given season. Henrik Moller also points out, ominously, that the southern colonies of sooties have been declining an average of 2% per year. For a bird that lays a single egg in a season and not every year, that is a path to extinction and mirrors the numbers that prodded the Key government into a small amount of action on that photo-opp CMF, kiwi (CMF? It’s a TLA; answers by email please). Maybe our role is just to hold the line on a small outpost colony until population-wide declines can be fixed (if we as a country care enough), rather than look to the sooties by themselves to turn Puangiangi into the seabird island it once would have been. We need to accept that the island is more likely to really get pumping seabird-wise if we can attract some fluttering shearwater or one of the other petrels (not forgetting little penguin and gannet as nutrient-bringers-in either) that are more common locally. This winter we put in some wooden boxes with plastic entrance tunnels at our flutterer speaker site, so that prospecting birds may be more likely to stay if they have somewhere weka-proof to shelter. It’s no coincidence the boxes are the same design as those on Mana and Matiu. Some of their flutterers might recognise the comforts of home when passing by and give them a go.

Lastly a bit of product endorsement which might be of interest to the seabird folk. We have had a long-term loan of the current state-of-the-art NZ-made burrowscope, but needed to give it back last year. Thanks Nicky Nelson, the loan much appreciated. They work very well, but run at $5000 and are quite bulky to carry around, albeit much less so than earlier iterations by other makers.

We had earlier tried out a little colour inspection camera sold to tradies, brand not remembered, which was pretty useless. For this season though, inspired by the videos on their site, I bought a specific inspection camera, the Tradesman Record from UK firm eazyview.com. This has proved to be at least the equal of its larger cousin. The screen is colour and has more than adequate resolution. It can also record photos and video clips, in my case usually accidentally as the record button falls rather too readily to hand. I suspect the daylight LEDs will lead to more false negatives than the infrared ones in big cousin, but it’s quick to deploy, get a handle on what the camera is showing and finish the burrow, so I think it will prove only as invasive as the big one, which Graeme Taylor has described as being about as disturbing to the chick as an adult returning to the burrow. The colour display is better at showing up downy chicks against dirt than the big monochrome instrument. It is easy to deploy and direct, with the flexible camera wand being of just the right stiffness to be controllable in the average to shorter burrows we have. The big one could not get any further than the new one down the longer burrows before we lost control of it. It’s more than possible to do a burrow by yourself, but we still prefer to have one person getting the wand into the burrow and the other watching the screen, as for the big burrowscope. Battery life is excellent, and we can do two months of checking 30 burrows, without recording, on a single charge of the 3 Eneloop Pro AAs (bought separately). Alkalines can also be used and there is a setting to select battery type so it doesn’t shut down early on the rechargeables. The supplied cheapie carry case protects the camera nicely and stuffs into a day pack easily. The afterthought pockets in the case are useless for spare batteries and the screwdriver you will need to change them, unless you like throwing small items down a hill in a dark forest when you unzip the case, but I suggest you get a little accessories bag and chuck that in the case instead. I haven’t managed to break it yet, or scratch the camera lens. It is also good for peering into kakariki nests (yes, there will be an article on kakariki some time soon).  Highly recommended, and landed in New Zealand for about $200. You will not notice the affiliate links at the bottom of this article, because there aren’t any. If I get excited about my new role as an influencer (hah!), then beware boot manufacturers (Lowa, I’m looking at you and your disintegrating rands).