predators

September 2 2019

Ashley Estuary Predator Trapping

ashleyriver black-billed gulls, cats, Predators, Trapping, wrybill birds, DOC 200, estuary, predators

The Ashley estuary is an internationally important wetland that hosts migratory national and international (e.g. bar-tailed godwit) species as well as permanent residents. Over 90 species of birds have been recorded. A Birds New Zealand 5 December 2018 survey in the estuary counted 348 birds including 320 waders, not including black-backed gulls that could have numbered in the hundreds. Only Lake Ellesmere had a higher count of wader species in Canterbury, but due to the large size and difficult access to that lake, ornithologists wanting to see a range of bird species always go first to the Ashley estuary. The estuary is also an important food source for braided river birds such as wrybill, black-fronted tern, black-billed gull and banded dotterel that breed higher up the Ashley River.

Ground predators (ferrets, stoats, weasels, hedgehogs, rats and feral cats) are the main threat to the birds – especially when nesting or at their juvenile stage. The trapping group (currently 9 members) was set up by BRaid to help extend the trapping programme that we run further downriver.

The estuary trapping group maintains 139 traps around the margins of the estuary. Most of these traps are DOC 200s, which can catch and humanely kill most predators except feral cats. An additional 16 traps specifically to kill feral cats have been sited away from houses so that pets are not targeted.

Since trapping began in July 2018 to late July 2019 a total of 290 predators have been caught.

January 14 2019

January 2019 update

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The last update was written in mid-November, and as that was mid-season, a fair bit has happened since then.

Annual survey. This, the key event of our bird year, went ahead on Nov 24, co-ordinated by Bev Alexander and Grant Davey.

As Grant says in his excellent report, “Eighteen volunteers took part, this was enough to do a quality survey. The weather was cloudy with some drizzle in the upper reaches. River flow was approximately 9 cumecs as measured at the gorge. A small flood reaching about 82 cumecs had occurred on 9 November and bird numbers may still have been recovering after this. A more significant flood soon after the survey (November 26), measuring up to 140 cumecs at the gorge, would have severely impacted bird numbers.”

Indeed, we were very lucky to get this survey completed when we did. If you want a copy of Grant’s report, I can send you one. In brief, total bird numbers were about the same as last year, so we have seen a couple of stable years, after the big declines in 2015 and 2016. This was due to weed invasion, and after last year’s major flood clearances we were hoping for higher numbers, but not so – probably because this has been a disrupted season. However, wrybill numbers were considerably up – from 9 last year to 20, with the long-term average being 13.

Interestingly, and demonstrating how dynamic are braided rivers and their inhabitants, if the annual count had been 2 days later (after the flood), wrybill numbers could well have been zero, as I have not seen a single wrybill on the river since that event.

Bird breeding. With a couple of exceptions, this season will probably go down as one of the poorest, due to the floods which occurred at sensitive times. Fortunately, 4 of our 8 wrybill pairs managed to fledge single chicks before floods intervened, but for other species virtually all eggs and non-flying chicks were lost to the Nov 26 flood. Also swept away by that event was a large black-billed (BBG) colony and some smaller colonies of black-fronted terns (BFTs). I thought that was the end of the season for them, but not so – the BBGs soon resettled not far up-river, with the BFTs a km or so further down. Needless to say, we have kept a close eye on them, with Grant drone-counting the gulls regularly. There are just over 1000 pairs, now at the stage of hatching chicks. The site is a good one, being a relatively weed-free island with good water currents on both sides. As the river flow declines, the terns are not so island protected, and the wet season means that they are in amongst rapidly growing lupins. Terns cannot be counted from the air (drone), but there appears to be around 60 present – so probably 20+ pairs, also now at the egg hatching stage. The gull and tern colonies are all that is left of breeding birds on the river, so we cross fingers for a successful outcome.

Predators. Despite having over 180 traps out on the riverbed, the predator catch over summer is often low, and such is the case right now. Catches increase in the autumn / early winter as young animals are kicked out of parent territories and food becomes more scarce. The Group is currently reviewing its trapping, with the aim of having all the riverbed margin covered from around the estuary right up to the Okuku junction – a distance of over 20km. This will require over 150 new traps – so Geoff will be approaching our trap-making team in the near future. Even though we will always rely largely on volunteers, we have to face the reality that servicing a large number of traps (well over 300) will require a new approach – involving some professional input.

Weeds. The 2017 major floods did a superb job clearing weeds, and vastly increased the areas of clean shingle which are absolutely vital for successful bird feeding and breeding. However, the floods brought down a new load of seeds, and these cleared stretches are rapidly being recolonised. Without doubt, our major challenge in the near future is how to keep the core bird breeding sites clear of weeds. Aerial spraying would be the most cost-effective means, but use of chemicals in waterways will always be controversial, and we do not want to go that way. This autumn we may well ask for volunteers to clear key sites. Although only small areas can be treated this way, it is almost the only volunteer-team exercise we can easily organise out on the riverbed – and if there is a good turnout, the results are always more impressive than initially imagined. Machinery options are being explored for larger areas.

Humans. As stated in the last Update, it is pleasing to report that disturbance by people and their machines has been relatively minor so far this season. Compared to 5+ years ago, it is relatively uncommon to see fresh vehicle tracks on the riverbed. All the same, there has been violations, one of which could result in a prosecution. I am sure that our signs and the access blockages are the major reason behind this good state of affairs. We are committed to removing the blocks in February, once the season is over.

Shingle extraction. We have always had great support from the major shingle extractor in the Ashley-Rakahuri riverbed – Taggarts Earthmoving Ltd. This year they have been working in the Hillcrest area, and we have spent much time monitoring bird activity within their concession site. Some of the nests found and followed have been within metres of regularly used tracks, so we have been able to collect useful data relative to how well-informed gravel extractors can work in close association with breeding birds.

Documentary video. Over the last year, we have spent some time compiling video material for documenting how the Group operates over a typical season. Tony Benny from Oxford (used to work on ‘Country Calendar’) was the film-maker, and has recently sent us a draft of the 20-minute product. This is in the final process of editing, and has impressed all viewers to date.

Meeting. We had a general meeting on Dec 10, with 13 folk in attendance.

Award. In the last Update, it was related how the Group had won the 2019 Practical Management Award offered by the Australasian Wildlife Management Association. In early December, I went over to Tasmania to accept this Award at the Society’s annual conference in Hobart. On the framed certificate we received, it is stated ‘In recognition of outstanding best practice in wildlife management’. The presenter commented that we won from a strong field of entrants. The following morning I spoke of ARRG activities to the 180 conference attendees. We are fortunate that the AWMS goes out of its way to support applied conservation research and management. Consequently, they liked what we had to say, and a couple of subsequent speakers referenced us as the sort of community group they wanted to support. A number of attendees came up to me afterwards with positive comments and interesting questions. The conference covered a wide range of conservation topics, but as many of the over 100 presentations illustrated, the conservation challenges in Australia are quite different to ours – mainly as there are many mammals involved, plus a different set of predators. They do not have any mustelids or hedgehogs (and foxes only on the mainland – none in Tasmania). The most talked about predator of interest to us was the feral cat, which is arguably their major problem.

Coming up. With the season coming to an end, the focus moves to writing up results and preparing presentations for a shorebird workshop up in the Firth of Thames area (organised by the Pukorokoro-Miranda Naturalists’ Trust) in March, and another braided river workshop (organised by BRaid Inc) out at Lincoln in June. We are also setting up to review our trapping and weed control systems. Relative to the latter, look out for notification about weed control workdays this coming autumn. This will be one of the few opportunities for many members to get out there and do their bit.

January 7 2019

ARRG wins a trans-Tasman award for practical wildlife management

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Conservationists throughout Australasia have recognised the work of the Ashley Rakahuri Rivercare Group (ARRG), to protect the unique braided river environment of the Ashley-Rakahuri River.

ARRG have won with the Australasian Wildlife Management Society (AWMS) annual award for practical wildlife management.

Out of eight finalists from throughout Australasia, the North Canterbury Group won the award for its practical work to protect and enhance the populations of endemic braided river birds in the Ashley-Rakahuri River, including such threatened species as the wrybill, black-fronted tern, black-billed gull and the banded dotterel. All of these birds nest on clean shingle banks and islands within the river environment.

“What I like about this award,” says ARRG Chair Nick Ledgard, “is that the judges would have known nothing about us before we entered, so we were competing in a ‘clean slate’ arena”.

For 14 years, ARRG has run a predator trapping programme along an 18km stretch of the Ashley-Rakahuri River from just West of Rangiora to where the river crosses state highway just north of Waikuku Township. Additionally, the group has annually surveyed the population of braided river birds in the protected area, compiling an important record of bird population and nesting success data. It has also conducted extensive public awareness campaigns to advocate for the protection of the riverbed and its inhabitants. One of the results of its advocacy is a local agreement to keep off-road vehicles out of the river during the bird breeding season.

“On the award certificate,” Nick says, “it reads, ‘in recognition of outstanding best practice in wildlife management’. We were told we had won from a strong field of entrants. The AWMS goes out of its way to support applied conservation research and management. I was told we were exactly the sort of community group they wanted to support.”

There were more than 100 presentations at the annual conference and it was clear conservation challenges in Australia are quite different to ours because of the presence of native land mammals in Australia, an issue New Zealand does not have (apart from two species of bat).

“The most talked about predator of interest to us was the feral cat, which is arguably their major problem and, of course, in a river that runs through urban areas such as Rangiora, a major problem for us too.”

Nick adds that one of the main ideas he took from the conference was the use of trail cameras to not only measure the activity of the protected animals, but also of their predators. “The trail cameras show behaviour we don’t normally get to see. This is particularly the case for feral cats which are most active at night. Knowing how, where and under what conditions feral cats predate our birds would be a great help in designing methods to maximise our control of these predators.

“I was also shown some thermo-imaging cameras. Open riverbeds would be ideal for these, and at night we could get to know every visitor (right down to mice). But the cost is still huge for the best gear and obtaining funding for such equipment would be too much for us.”

When asked what he considered to be ARRG’s biggest challenge for the future, he replied, “I felt it was keeping on top of invasive weeds, which can quickly reduce suitable bird feeding and breeding habitat. Our surveys show that we can keep on top of the predators in the controlled area with trapping, but weed control is an ongoing and repeated issue if we are to maintain the clean shingle areas the birds need to breed.”