Down on the river
The main gauge of our success in looking after the indigenous birds on the river comes from our annual surveys of species numbers. This season, the survey took place on November 21, and is well reported in Grant Davey’s report (2020 Ashley-Rakahuri Annual Bird Survey). The total of wrybill, banded dotterels (BD), black-fronted terns (BFT), pied stilts (PS) and S. Is pied oystercatchers (SIPO) was 376 compared with 1004 last year and 461 in 2018. This was the third equal worst year on record (along with 2002) for these species – with the worst year being 2001 (285 birds). Before thinking ‘all is lost – we’ve failed’, consider this. Numbers plummeted after 2014 due to lack of large floods and a major expansion of invasive weeds. The 1-in-10 year flood of July 2017 brought the weed situation back to above the 2014 level and we thought the high 2020 survey figures indicated a great recovery. However, we now know that the exceptional bird numbers of that year were without doubt strongly influenced by floods in the Waimakariri forcing birds to move elsewhere. Right now the weeds are again advancing vigorously, so until we win that battle (see ‘Loss of habitat’ below) the bird numbers are likely to remain in the recovery phase. On the positive side, black-billed gull (BBG) Sept 21 survey numbers were 1820 (this species is not included in the above figures as a single colony can distort all-species comparisons), the second highest on record, and at the Smarts site BBG numbers had risen to 2846 a month later. Until relatively recently we had a BBG colony about every second year, but since 2016 a reasonable local colony has been an annual feature. At the time of writing, BBG numbers at the Smarts site (around 4ha) are 1780, of which around 1280 are flying juveniles. This would be one of our best ever BBG fledging results. The island site was cleared of weeds by a Taggart Earthmoving shingle extraction operation over the 2020 winter, and in addition to the large BBG colony, has attracted breeding BFTs, BDs, PSs, SIPOs and a single wrybill pair. As such, the site represents a vision of what bird life on the river can be, and this could certainly be improved further, plus hopefully replicated elsewhere (see below). At least 8 wrybill pairs took up territories over the season, which is the same as 2 years ago, and only a couple less than last season. Most of these hatched and fledged chicks. The species which remains of most concern is the BFT. Survey numbers were the fourth lowest on record, and their breeding success has once again been poor. Small colonies established to the nest/egg stage at 4 locations, but only the one at Smarts progressed to hatching chicks. Our monitoring of the Smarts colony this season has been mainly undertaken by Grant Davey, who regularly checks nests and traps in addition to aerial counts using our drone. The Group is extremely fortunate to have access to Grant’s data gathering and processing skills. I doubt if any other similar conservation entity in the country collects and publically presents such detailed results with such accuracy, clarity and promptness. For some weeks, Grant was greatly assisted by an ECan student intern, Matt Kim, who enjoyed spending hours observing the birds from our hide on the north bank of the river.
Loss of habitat
This remains our biggest challenge, and influences bird populations the most. The major concern is the rapid invasion of weeds – mainly lupins, gorse, broom, blackberry and willow, plus a range of grasses and other herbaceous species. The Smarts site, where bird breeding has been good, is a good example of this problem. It was virtually clear of weeds in September, but is now well covered in a new crop of seedlings. Weed invasion not only ruins bird breeding sites, but also smothers important shallow water/shingle margins where most feeding occurs. Nothing other than artificial clearing can be guaranteed to change this, as we cannot depend on natural floods. Last winter we cleared over 40 ha, mainly with a custom-built tractor-mounted undercutter. This coming winter we must do more of the same at selected sites which birds favour for breeding and feeding. Loss of open braided river habitat has also occurred as the berm zone (there to protect the stopbank) has expanded out into the open fairway – where birds feed and breed. As clearly stated in our 2019-20 annual report, over 50% of the fairway has been lost since 1942, and it continues to shrink to the present day. Excessive shingle extraction does not help to retain braids as it causes deepening and channelling of flow pathways. Discussions are underway with river engineers as to how this past management can be amended to enhance the ‘natural’ braided river character and extent of the Ashley-Rakahuri river. All this is part of a long-term planning process funded by ECan, and promised for consultation in the near future.
This is by far our major commitment in terms of personnel involved and operational hours – and continues all year round, both alongside the river and around the estuary. There is a total of just under 400 traps out there, serviced at least monthly by 25 volunteer trappers. Since July 1, 2020, trap-catch figures alongside the river read 10 cats, 63 hedgehogs, 21 weasels, 8 stoats, 1 ferret, 8 rats, 18 ship rats and 25 Norway rats. Whilst at the estuary – 2 cats, 3 hedgehogs, 15 weasels, 17 stoats, 0 ferrets, 10 ship rats and 13 Norway rats. Last season, our large BBG colony at the Railway site suffered major predation by rats and harrier hawks. This year, only 2 Norway rats and a mouse have been trapped on Smarts island (compared to about 15 rats and a stoat last year), and raids by harrier hawks appear to have been minimal. The latter could well be due to scarecrows erected close to the colony. On December 11, a trappers BBQ was hosted at the DOC offices, attracting over 30 participants.
The main way to reduce this is by making sure the public are well informed – via media articles, presentations and talks, displays, and our website and Facebook page. We now have a Promotions / Communications strategy, drawn up by professional advocacy member, Steve Attwood, and implementing that is a newly appointed Promotions Officer, Joan Miles. Our awareness efforts must be working, as compared to the past, this season has seen far fewer people and vehicle intrusions out onto the riverbed.
Apart from talking to groups, making presentations and manning displays, we accompany visitors to see what is actually happening on the river. Over the season, we have had visits by those who have gifted donations, ECan engineers and riverbed staff, the Waimakariri Zone committee, an Orari Rivercare Group rep, a TVNZ crew and our Mayor, Dan Gordon. All appear impressed by what they see, and are very supportive for the continuation of our efforts.
The Group is always closely following its accounts and budget situation – and generally our finances are in good shape. We are now mostly self-funded for our day-to-day existence, with monies coming from donations, our trap making and selling, and sponsorship via Karikaas Natural Dairy Products Ltd cheese sales. Funds for larger special projects, such as weed clearing, come from ECan.
Our 8-person Management Committee met on December 1, followed by a general meeting on December 3. The MC will meet next before the end of this month. Please mark Thursday, March 18 on your calendar for our next General meeting – starting at 7pm at the DOC offices on River Road.
As usual, many thanks to all our volunteers for the time taken to support our cause.