annual survey

September 13 2023

Group Update, September 2023

ashleyriver 4X4, annual survey, black billed gulls, black-billed gulls, black-fronted tern, management, research, Trapping, weeds, wrybill

One of the first indications of an imminent nesting season is the arrival of wrybills at the estuary – destined for not only the Ashley River, but other rivers to the south. This year they were first noted on 19 August and have occurred in flocks of up to 31. Amongst them have been 7 birds that we have banded up the river in the past – last year, the season before, or in the case of BWBW – quite a few years ago. Some of these have been seen several times, one (KOWY) was there for about a month.

We have counted only about 7 wrybills along the river so far, these have been in the usual nesting areas off Groyne 2 and Smarts. Nests have yet to be found.

Banded dotterel have been slow to arrive at the estuary and along the river. But on 11 September there were 8 in the area where they nested last year in the estuary east of the Kings Ave entrance and 5 at the Smarts area along the river. One of our new members has found 2 BD nests in the river up near the gorge.

Black-fronted terns won’t be nesting until early to mid-October, but they have been gathering in places along the river and where the river meets the estuary. A week ago, there were about 70 off the Swamp Road river entrance.

For several weeks black-billed gulls have been gathering, sometimes in numbers of around 500 – 600, just downstream from the Cones Road bridge. They don’t appear to be nesting as yet, and could well move on to somewhere new.

Preparations for the nesting season have included weed clearing, river entrance blocking and a rat detection dog effort against Norway rats.

Using funds provided by the Waimakariri Zone Committee and ARRG, in July we cleared 27ha of weeds using the tractor mounted ripper made and owned by Cresslands Contracting. Our first targets were high islands which had been nested on before, then other weedy islands, but also areas of quite thick weed – mainly lupin. The machine worked well on flat areas with lupin, but not so well where there were small gorse plants or where the ground was uneven. There was a significant flood on 23 July (394 cumecs at the gorge) which covered most of the fairway and also cleared a lot of weeds – weeds will not be an impediment to nesting this season. This flow was enough to change the layout of the river, with fewer braids and less shallow feeding habitat remaining, perhaps this will cause a reduction in bird numbers. Smaller floods will hopefully improve the habitat during the nesting season, but they may also wash away nests.

In early August, Leona Kirk of Wildlife Protection Services used her rat detection dogs along the south side of the river. The aim was to try and find and deal with Norway rat colonies before they could affect the birds. Norway rats are our most destructive predator. The most signs of rats were found on trap line F (westernmost line on the south bank), where the most Norway rats had been caught in the last year. The dogs indicated the presence of rats in a burrow which had been excavated into a muddy bank. This was dug out, but only went for a few metres and no rats were found. Evidence of rats (scent, tracks etc) was found out on the riverbed in several places – where the rats seem to have ventured after the flood in search of food. Trail cameras were placed at 3 of these sites, and rats were seen on photos.

We followed this up with a few hours of loader time (Cresslands) to try and dislodge them from piles of debris or burrows along banks, but none were found. We couldn’t use the loader in all the planned locations due to boggy conditions. Despite the lack of rats killed, we have learnt some valuable information. As suspected, Norway rats burrow into banks, especially muddy ones – but they also take possibly short-term refuge in debris piles. They do not appear to be present in large colonies along the river, and seem to move around quite a lot. This makes them more difficult to deal with than hoped for.

In the first few days of September most of the access points to the river were blocked off – in a very satisfactory joint venture between ARRG and the ECan Parks section (top image). We scout out locations to be blocked (this year with an ECan ranger) ECan provide and transport new blocks – and organize and pay for a digger to install them, and we supervise the installation. They will remain in place until February next year. This year 17 new blocks were needed (top image). In a few places banks were steepened up to deter 4wds. There are still many places where motorbikes can get out on the river.

There are several new trappers with river lines. Predator catch hit a new record in the August 2022 to July 2023 season. This was partly due to 102 extra traps funded by ECan and managed by Excell Biosecurity, and partly to the ongoing Ship rat boom. Catch rate increased in the estuary traps for the first year since we started trapping – in 2018.

The annual report is almost complete.

To mark the 100^th birthday of Forest and Bird, Bird of the Year is this year Bird of the Century. The black-fronted tern is a candidate, and the photograph they are using is of a bird from the Ashley. Please vote BFT.

Our annual bird count is on 18 November this year.

At the estuary –

Eleanor Gunby is carrying on with her MSc thesis work – with further funding provided by the Waimakairiri Zone Committee through ARRG.
This season there seems to be even more human disturbance. The Waimakariri District Council is reviewing the Northern Pegasus Bay Bylaw and will be asking for public submissions, probably from mid October to mid November. We would like to tighten rules around dogs and vehicle access.
As a result of ARRG advocacy, ECan is going to be doing some work on the Southern Black-backed Gull nests at the estuary. Along the spit, and probably along the western margin of the estuary, eggs will be broken and nests destroyed. Last season SBBG were responsible (along with disturbance) for the inability of BD to nest along the spit, and for the destruction of a white-fronted tern colony.
Bev Alexander is giving a talk on estuary birds for the Waimakariri Biodiversity Trust at the Waikuku Beach hall from 7pm on 13 September.

Grant Davey

11/9/23

February 20 2022

Group Update, February 2022

ashleyriver annual survey, black billed gulls, black-billed gulls, black-fronted tern, management, research, Trapping, weeds, wrybill

The last Update was written in August 2021, so much has happened since then. The main events have been our annual bird survey in November, and our monitoring of a full 2021-22 breeding season. It is these two activities which are key to determining whether we are succeeding in our mission of ‘protecting birds and their habitat in the Ashley River/Rakahuri’.

The birds

Annual survey. The 20 November Ashley-Rakahuri (A-R) survey attracted a record number of 23 people, who covered the 21km between the Okuku confluence and the SH1 bridge in 4 groups – most finishing by 1pm. The numbers of birds counted are shown in the figure above (prepared by Grant Davey).

This appears to show a recovering population, heading back towards the highest numbers of 2014. However, we are suspicious about this, as close observation on the river prior to the survey indicated far fewer birds. We think the explanation is connected to floods in the Waimakariri at the time of the survey, which caused birds to retreat to the A-R. Whatever the reason, there were record numbers of nearly all species. The total wrybill count was 30, higher than the previous record of 27 in 2019 (which was also a year when birds were being flooded out of the Waimakariri). Without this invasion, the low numbers of the last few years in the Ashley would almost certainly have continued. But it does show the importance of the A-R as a flood haven for birds washed out from the much bigger main divide-fed rivers.

Last year, our survey data since 2000 was sent for consideration by a national panel reviewing the NZ Threat Classification System. As they said in a ‘thank-you’ message, such long-term datasets are extremely valuable. From our data, they calculated that the numbers of black-fronted terns seen on the A-R have increased significantly, by an average of 5.4% per annum; wrybills have increased by 3.8%, and banded dotterels by 1.8% (although they have declined since 2015 – as seems to be the case nationally). Black-billed gull numbers have also increased markedly. We used to have a breeding colony only every 2-3 years, whereas they have turned up almost annually since 2016. We will never know exactly, but our management is likely to be behind these increases in bird numbers on the A-R.

The breeding season. Due to the record floods in May/June last year, the birds returned to find an almost weed-free A-R. Such disturbance to core aquatic insect food sources may have been a reason why the season got off to a slow start. But we ended up with 13 wrybill taking up territories – the previous highest being 10. Eight chicks fledged to give a productivity of 0.62. This is the most pairs and the second most fledglings on record, but productivity was below average. We located 96 black-fronted tern nests, but only 11 fledglings have been seen, mainly due to predation. Entire colonies were lost to rats, plus a flood did not help. Consequently, many nests would have been second attempts, some perhaps even third. Such fickle tern breeding has been par for the course over most years, and it is surprising that overall numbers have actually increased. For the first time since 2016, there was no large black-billed gull colony on (or close to) the main riverbed, but a large colony of many hundred nests formed (twice) at the estuary. The second effort was successful, with many hundreds of fledglings produced. Our other focus species (banded dotterels, pied stilts and South Island pied oystercatchers) appeared to have reasonable seasons, but too few nests were found to measure success. We plan to monitor them more closely next season. Plus we hope to engage a student to start monitoring bird breeding around the estuary (never done before).

Maintaining habitat

Weed invasion. This remains our greatest threat, as although the record May/June floods swept the riverbed clean, the weeds have rapidly returned. We have been meeting with ECan to discuss how we can remove weeds while they are small (with most yet to seed). The recent good February flood did more clearance, and we plan to clear much of the rest from favoured areas within the next 2 months. If successful this would be a major advance in management. Once the large operational clearances have been completed, we could well use volunteers to hand clear the gaps.

Gravel extraction. This is the main commercial activity undertaken on the river. Although gravel extraction can assist the birds by removing weeds, there are many examples which show that it can also create problems if not carried out properly. We are not happy with recent consent applications, and the history of compliance monitoring being carried out appropriately is not good. Plus, and perhaps most importantly, safety aspects associated with gravel extraction need improvement. These concerns have been pointed out to ECan, and it may be that, in order to bring about much needed changes, we have to go more public in the near future.

Flood control management. We fully agree that flood control should be the No. 1 goal, but we are concerned about how this is being carried out. All experts agree that in order to maintain the characteristic features of a braided river, it must be given room to move, but current management has resulted in excessive berm planting, which is leading to the A-R fairway becoming overly constricted. ECan has recently made environmental considerations a much higher priority for management, and we are to be involved in discussions to this end, so we are hopeful of changes in the right direction.

Predator trapping

This remains our major commitment in terms of personnel and operational hours involved – and continues all year round, both alongside the river and around the estuary. Currently there are 182 traps along the river and 102 at the estuary, serviced at least monthly by 26 volunteer trappers. In addition, during the season, there are around 60 traps (mostly run-through DOC150s) managed separately around breeding birds. As the discussion below indicates, even though the current trapping effort remains significant and important, we know we should be having a greater impact on predator numbers.

Trap catch. Alongside the river. Despite the consistent trapping effort, results show that the trap-catch rate has been static over recent years – at around 0.5 predators caught per 100 trap nights. Over the last 3 years, we have caught more than half the total number of predators since we began trapping in 2004. At that time, the major catch was hedgehogs. These still remain predominant, but have been joined in recent years by rats, which were rarely caught before 2016. Ship rats have been responsible for nearly all bird losses over the past season. It is interesting to note that stoats were slightly more common than weasels until around 2016, but have well outnumbered the former ever since.

Around the estuary. The composition of predators caught alongside the river is very different to that caught at the estuary. Compared to the river, the estuary has a higher percentage of rats (54% estuary; 37% river), stoats (14%; 6%) and weasels (22%; 14%), but a lower percentage of hedgehogs (6%; 34%) and feral cats (4%; 9%). The reasons for this are unknown. We have only been trapping around the estuary for 3 years, but it appears that the catch is decreasing over time. This could be due to our trapping, but it could also be because we have a much greater trap density than along the river

How effective are traps? As mentioned in the August update, we have long suspected that many predators visiting trap sites do not get caught. A trail camera/trap project undertaken a year ago by a student, Quill Yates, confirmed this. Almost 20,000 images were analysed. The main finding was that only 8.3% of predator visits resulted in successful catches. The percentage caught / visit for feral cats, rats and hedgehogs were 2%, 22% and 23% respectively. The traps had visits from 50 cats, and Quill went to some trouble to identify 20 different individuals. Only a single cat was caught, even though on 35% of visits, they put their heads into the Timms trap openings but did not trigger them. Too few mustelids (ferrets, stoats and weasels) were caught to allow for any analyses to be done.

Trapping review. A year ago, ECan agreed to fund a review of our trapping strategy, including the possibility of doubling our trap numbers by installing a double line alongside the river. A contractor has just completed this review which should be available for reading in the near future.

Public relations and human disturbance on the riverbed

We continue to make sure the public are well informed – via media articles, presentations and talks, displays, Facebook and website. How we manage the latter is currently being reviewed. It is well worth listening to our monthly interviews on the local CompassFM radio station. A large new interpretation panel will be erected by the Cones Road bridge picnic area in the near future. As in previous seasons, 4WD access ways which were blocked in September, have just been cleared. There is little doubt that this has resulted in significantly less vehicle disturbance during the past breeding season.

Finances

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 usually come from ECan.

Reports

For over a year, ECan has been drafting a long-term management plan for the Ashley-Rakahuri River. This will be available to us within the next 2 months, and should shape where we head in the future. The annual report for 2020-21 has been completed and is now available. Internally, there have been a number of other reports written, mainly by Grant Davey.

Group structure and meetings

In addition to the normal committee hierarchy of chair, secretary and treasurer, we have created three management teams – operations, communication and administration. It was felt that such a structure will lead to less work required by any one individual. At our last AGM, the Group chair, Nick Ledgard, stepped down after 20 years in that position, to be replaced by Sue Mardon. More recently, our Secretary, Joan Miles, also retired after 20 years of service to the Group. In the near future, we plan to have a SWOT (strengths, weaknesses, opportunities, threats) gathering, in order to review our composition and where we think we should be headed.

As usual, many thanks to all our volunteers for the time taken to support our cause.

Sue Mardon

Chair, ARRG

August 23 2021

Group Update, August 2021

ashleyriver 4X4, annual survey, black billed gulls, black-billed gulls, black-fronted tern, floods, management, Predators, research, Trapping, Trapping, weeds, wrybill

by Nick Ledgard, ARRG Chair

The last Update was written earlier this year in January, so a fair bit of water has gone under the bridge since then. Quite literally actually, as the most significant happening affecting our local river over the last 6 months has been the record floods of late May and mid June.

Down on the river. The floods not only cleared the riverbed of virtually all weeds, but also ate into the margin of the vegetated berm which lies between the open fairway and the marginal banks. This has widened the fairway in places, but it may well be less braided than before. Despite the floods, the berm remains considerably wider than it was a few decades ago, and as stated publicly many times recently, a braided river must have ‘room to move’ in order to maintain the braided riverbed habitat which the birds need for successful breeding and feeding. Although we now have a ‘weed-free / clean slate’ riverbed, the future challenge is how to keep it that way.

Bird movement. After February, our core indigenous breeding bird species (wrybill, black-fronted tern (BFT), black-billed gull (BBG), banded dotterel (BD), pied stilt and S. Is pied oystercatcher) move out to warmer winter locations. Most retreat to the coast and the northern N. Island, whilst some of the banded dotterels cross the Tasman Sea to Australia. Over winter, only a handful of other species, including a few BFT, remain on the river. We have good records of these, as some sections of the riverbed are walked at least monthly by Grant Davey and myself.

Right now, the breeding birds are starting to return. The first wrybill was seen on August 16, and we can expect to find nests from around mid-September. Small numbers of BD, BBG and BFT have also been seen, and some BD may be nesting as they are usually the first to start. Nesting colonies of the gulls and terns are unlikely to be established before mid-October. The May/June floods mean that there are many weed-free sites available for breeding, but that major disruption which was followed by a number of other high flow events may result in a slower than usual return of core foods – aquatic insects and small fish.

Maintaining habitat. Weed invasion remains our greatest threat, as although the record May/June floods swept the riverbed clean, the weeds will rapidly return. Initially, they will be small and more readily removed, so we have new opportunities for sorting out the cost-effective means of controlling them. The riverbed is owned by ECan and understandably, the prime aim of past management has been on flood control. This has sometimes been at the expense of conservation values, such as bird habitat. Hence, over the last year, we have had many discussions about shifting the management focus more towards environmental considerations.

Gravel extraction. This is the main commercial activity undertaken on the river. Although such activity can assist the birds by removing weeds, there are many examples which show that it can also create problems if not carried out properly. In our discussions, we have pointed these out to ECan, who are keen to correct consent deficiencies and improve their oversight. They are very aware that we spend more time on the riverbed than virtually anyone else, and so can act as watchdogs. Gravel extraction has been considerable (some would say excessive) over recent years. It is likely to become more restricted in the near future, as despite the recent floods moving masses of gravel down-river, very little of this is ‘new’ ie., originating from catchment headwaters.

Predator trapping. This remains our major commitment in terms of personnel and operational hours involved – and continues all year round, both alongside the river and around the estuary. Over the last year there have been on average 236 traps along the river and 129 at the estuary, serviced at least monthly by 26 volunteer trappers. Nearly 100 traps were lost to the May/June floods, but thanks to generous cash donations and supply of materials, the majority of those have now been replaced. We are particularly grateful to the Mens Shed at Rymans Healthcare village who have made nearly all the replacement DOC200 boxes.

Trap catch. Over the past 2 years, we have trapped almost 1000 predators, with the dominant species being hedgehogs and rats. However, despite the consistent trapping effort, results show that the trap-catch rate has been static over recent years – at around 0.5 predators caught per 100 trap nights. The composition of predators caught alongside the river was very different to that caught at the estuary. Compared to the river, the estuary had a higher percentage of rats (53% estuary; 35% river), stoats (16%; 6%) and weasels (18%; 11%), but a lower percentage of hedgehogs (9%; 38%) and feral cats (5%; 10%). The reasons for this are unknown.

How effective are traps? We have long suspected that many predators visiting trap sites do not get caught. In order to look more closely at this, we set up a project for a student, Quill Yates. He investigated predator visits and catches over a 2-month period last autumn. Trail cameras were set up at three sites where three trap types were placed alongside each other. Almost 20,000 images were analysed. The main finding was that only 8.3% of predator visits resulted in successful catches. The percentage caught / visit for feral cats, rats and hedgehogs were 2%, 22% and 22% respectively. Too few mustelids (ferrets, stoats and weasels) were caught to allow for any analyses to be done. A detailed report is being written, which will contain recommendations as to how the number of trap-catches might be improved.

Trapping review. A year ago, ECan agreed to fund a review of our trapping strategy, including the possibility of doubling our trap numbers by installing a double line alongside the river. A contractor has been approached to undertake the review.

Human disturbance. We continue to make sure the public are well informed – via media articles, presentations and talks, displays, and our website and Facebook page. In the 2020-21 year, there were 39 different promotion activities undertaken. Earlier this month, all 4WD access ways were mapped, and as in previous years, these will be blocked during the breeding season (September to the end of January).

Finances. 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 usually come from ECan.

Reports. For over a year, ECan has been drafting a long-term management plan for the Ashley-Rakahuri River. This will recommend how we carry on into the future. It is hoped to be able to read this report in the near future. The annual report for 2020-21 will be completed within the next month. This, and a number of internal reports (referenced in the annual report), are written by Grant Davey and myself.

Group structure and meetings. In addition to the normal committee hierarchy of chair, secretary and treasurer, it was agreed in June to create three management teams – operations, communication and administration. It was felt that such a structure will lead to less work required by any one individual. The teams will be confirmed at the 2021 AGM on October 7, together with the member(s) to lead each of them. Our 8-person Management Committee continues to meet regularly.

Finally, this will be the last Update that I write as Chairman. After 18 years in this position, it is time to hand over to someone else.

As usual, many thanks to all our volunteers for the time taken to support our cause.

Nick Ledgard
Chair, ARRG

January 17 2021

Group update Jan 2021

ashleyriver 4X4, management, research, Trapping, weeds, wrybill

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.

Trapping

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.

Human disturbance

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.

Visitors

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.

Finances

Meetings

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.

Nick Ledgard

Chair, ARRG

November 28 2020

2020 Annual Bird Survey

ashleyriver annual survey, black-billed gulls, management

Title image: Key braided river bird locations: 2018, 2019, and 2020.

A PDF of this report is available here

Introduction

The Ashley Rakahuri Rivercare Group (ARRG) has an unbroken 21-year history of annual bird counts – running 19km from the Okuku junction to State Highway One. For the last 3 years we have also included the 2km section from SH1 to the top of the estuary and have counted the birds in 1km stretches of the river. This counting method has now been standardized across Canterbury. The graphs (other than that for the black-billed gulls) and numbers in this report show data that excludes the lowermost 2km of the river.

On 21 November this year we had 22 active participants in 4 groups on the usual river reaches – starting at about 9am. In the early afternoon 2 surveyors did the 2km down to the estuary. There was a weak to moderate northwesterly wind, cool conditions, and river flow of about 8 cumecs at the Ashley gorge (Figure 1). There had been a small flood of 50 cumecs on 8 November, this was enough to wash away some black-fronted tern nests near Groyne 9 and near Cones Road bridge – but the birds would have had time to re-nest before the survey.

Figure 1. River flow at Ashley Gorge

This year most participants had radios, although a few were faulty or had insufficient battery life. Radios improve communication considerably and should lead to less double counting.

For the past 3 years we have counted black-billed gulls in colonies using drone photographs – this year the day before the survey. This leads to considerably more accurate numbers, and almost inevitably higher ones than would have resulted from a land count.

Overall Numbers and Bird Locations

The 6 key braided river bird species that we are most concerned about are wrybill, banded dotterel (BD), black-fronted tern (BFT), southern pied oystercatcher (SIPO), pied stilt (PS) and black-billed gull (BBG). Numbers since 2000 of the former 5 species are plotted on Figure 2 and Figure 3 with BBG on Figure 4 – as the BBG numbers tend to overwhelm those of the other species when plotted on a graph.

Figure 3. Annual bird count results, key braided river species, 2000 – 2020

Figure 4. Annual bird count results, black-billed gulls, 2000 – 2020

Some observations:

The total of wrybill, BD, BFT, PS and SIPO was 376 compared with 1004 last year and 461 in 2018. Last year was however an exceptional year with bird numbers doubtlessly strongly influenced by floods in the Waimakariri.
2020 was the third equal worst year on record (with 2002) for these species – with the worst year being 2001 (285 birds). This result no doubt partly reflects the regrowth of weeds since the July 2017 1 in 10-year flood. In July-August this year ARRG (with ECan funding) cleared weeds from 40 ha of islands. This should have given enough space for colony (BFT and BBG) and territorial nesters. Perhaps the overall weedy nature of the river is a deterrent to the birds, and no doubt there are other local and external factors at play. Nesting conditions may have been better on the Waimakariri this year, and possibly food is a factor.
Black-billed gulls do not appear to have been affected by any adverse conditions – note that Figure 4 shows the 2018 colony that was just below the SH1 bridge at the time of the survey. This got washed out and the birds moved several kilometres upstream soon after the survey.
This season weekly bird counts have been done by GD between Cones Road and SH1 – Figure 6. The last bar on this figure shows results from the annual survey, and with the exception of BD, numbers are very similar to the previous count a week before which was done with a lot of zigzagging and back and forwarding.
Figure 7 (to of this page) shows the kilometre by kilometre locations of the key species in the years 2018, 2019 and 2020.

Figure 5. Key species counts – Cones Road to SH1, 2020, weekly surveys

Figure 6. Key species counts – Cones Road to SH1, 2020, weekly surveys

Figure 8. Other river bird locations, 2020

Of note are –

Quite large numbers of birds, especially PS and BFT, eastward of SH1. This is a single channel reach with little bare gravel and trees close to the river – in reaches with similar conditions elsewhere along the river there are few braided river birds. This whitebait season there has also been a lot of disturbance in the area. Presumably the bird numbers here are due to food supply in the estuary and tidal part of the river. Perhaps lower numbers higher up the river this year could be partly due to poorer food supply there this year?
The relatively high number of birds, especially PS, north of where Smarts Road joins Tulls Road. This is an area of recent gravel extraction where Taggart cleared a large area of weeds. This is also where the BBG colony is.
Large bird numbers near Cones Road – this has been a favoured area for BD nesting this year and there is a small BFT colony. There has been less human disturbance than usual here this year, and there has been a quite large area of bare gravel.
Best bird numbers, with the greatest species variation, were off Groyne 2 (near the airport). This is the best-preserved section of braiding along the river and has been the favoured section for wrybill nesting for some time.

Comments on Individual Species

Wrybill

Ten wrybill were counted this year, this is considerably fewer than the 27 last year and less than the average since 2000 of 13. One bird seen between kilometres 3 and 4 had not been previously monitored this year. Only one wrybill was seen east of Cones Road when there were 2 nests in this area (at Marchmont and Smarts) this year. The Marchmont birds have not been seen since the small flood of 8 November. This should not have affected the large chick that they were guarding, but maybe it has been predated.

Most of the wrybill were seen in kilometres 6 to 8. None were found in the vicinity of Groyne 1 where a pair were successfully raising a chick just before the survey – however a few days later one was seen in this area showing chick guarding behaviour.

Last season 9 pairs of wrybills were seen on territories, this year there had been 8 pairs seen. Many of the 27 wrybill seen in the 2019 survey are likely to have been displaced by floods from the Waimakariri, and did not nest on the Ashley.

Banded Dotterel

The 133 BD counted this year was well down on the 323 last year and the average of 209. However, the northwest wind perhaps caused BD to be under-counted. Several times birds were seen up close, keeping low and not making noise when they would normally be expected to fly when approached. With this behaviour, and sometimes quite widely spaced surveyors, some birds would be missed. shows evidence for this undercounting – there was an unexpected drop in BD numbers eastward of Cones Road from the week before the annual survey when numbers of other species remained very much the same or slightly higher. Tightening up of survey procedures, leading to less double counting, could also cause numbers to drop. The way BD circle around out of their territories when disturbed makes them prone to double counting.

Several BD chicks were seen in the survey, but perhaps not as many as should be expected. Early in the season a number of BD nests were found and monitored, most of these were not successful. One was lost to a small fresh and one to a harrier – caught by trail camera.

BD were most common in the few kilometres downstream from the Okuku junction and near Cones Road.

Black-fronted Tern

The 65 counted this year was the fourth lowest on record, 2005 (26), 2004 (28) and 2001 (44) had the lowest numbers. In 2019 there were 296 counted. BFT numbers were the most reduced of the key species compared to 2019. Numbers do seem to have increased slightly eastward of Cones Road in the few days after the survey – with some more nests having been made.

This looks to be a very poor breeding season for BFT – although there is still time for some to nest. At the time of the survey nesting seemed to be taking place only in 4 locations – very close to the Cones Road bridge (only a handful of nests), on the Smarts island where Taggart cleared weeds (2 clusters of maybe 3 nests each) and probably a few nests immediately above the estuary. Prior to 8 November there had been a good colony off Groyne 9 – with around 20 nests mainly on an island that ARRG had cleared of weeds this year. Some of these nests were abandoned prior to the small flood of 8 November, some were washed away in the flood, and some were abandoned at this time despite not being flooded. The reason for the abandonment is not known – although there had been 4wd and motorbike activity through the colony despite signage. During the day the vehicles weren’t causing abandonment, but at night they could well have done. These birds have had time to renest in this area after the flood, but have not done so.

Figure 5 shows that eastward of Cones Road BFT numbers have dropped steeply since late September. The birds were here, but decided to nest elsewhere. Reasons for this are not understood, there appears to be enough bare gravel for them to nest – areas that ARRG has cleared and others – including a large naturally clear area near Groyne 4 where there was a big BFT colony in 2019. Perhaps the answer has to do with food supply. Birds have been captured on trail cameras bringing worms to nests, not the more usual whitebait.

Black-billed Gull

On 18 November 1820 were counted from drone photos at or near the colony on Smarts island. – with just a few elsewhere along the river – mainly near the estuary. This is the second highest number on record – after 2019 when there were 4097. On 11 November there had been 2846 at the Smarts site, but numbers are following what now seems to be an established pattern – maximum numbers occurring around a week after inception of the colony, then many birds leave the area.

Nests have yet to be counted, but there are perhaps in excess of 1000.

Until relatively recently on the Ashley we have had a BBG colony about every second year, but since 2016 a reasonable local colony has been an annual feature. Figure 4 does not show the 2016 colony in a dairy farm paddock just southeast of the SH1 bridge.

Pied Stilt

This was the most abundant species on the river this year – although the total number at 141 was still less than the average of 163. This was the 10^th worse year on record for PS.

Stilt numbers increased significantly in the lower half of the river since August – Figure 5. In the survey annual they were seen to be most abundant near the estuary, at Smarts, Tulls and near Groyne 2. None at all were seen in kilometres 1 to 3 downstream from the Okuku junction. Their behaviour in most places showed that they were nesting.

Pied Oystercatcher

Twenty-seven SIPO were counted this year, down significantly from 2019, but essentially the same as the long-term average of 28. SIPO and PS are the least threatened of the braided river birds and nest in several other environments.

They were seen sporadically along the river. As with BD, they are early nesters and most of them probably had chicks. Two dead adult SIPO were seen off Groyne 9, they had perhaps been shot.

Black-backed Gull

Fourteen SBBG were counted, this compares with the long-term survey average of 11. All but one of these were seen between kilometres 12 and 19. In the previous twelve one person counts of this area this year, the average seen was 4, so this years annual survey result does not represent an increase in SBBG. These birds are a major predator of braided river bird eggs and chicks on other rivers such as the Waimakariri and Waiau – where they nest in large colonies. They also nest at the Ashley estuary, but for reasons unknown, they are quite rare further up the river. In the last 15 years only 1 SBBG nest has been found in the Ashley riverbed.

Black-fronted Dotterel

Seven were seen between kilometres 13 and 17 (Marchmont to Toppings). This compares with a maximum of 5 seen in the same area in the weekly surveys. A further bird was seen east of SH1. Black-fronted dotterels have been increasing in abundance in the last few years (only 1 counted in 2019) and have been seen further upstream as time goes by. They are usually found in sandy or muddy backwaters which aren’t classic braided river habitats. For years they have been well known in the Waipara river and are quite common in the Opihi. These rivers are degraded and channelized braided rivers and increasing numbers in the Ashley may not be a good sign.

Spur-winged Plover

Twenty-one were counted in 2020, this compares to a long-term average of 41. This species is highly erratic in distribution, sometimes occurring in large flocks, sometimes with only a few individuals. The maximum seen in a survey since 2000 was 149.

Water Birds

Ducks, shags, Canada Geese, white-faced herons and paradise ducks are found along the river but are not specifically braided river birds. They actually prefer deeper water channels that run along the edges of the fairway close to trees – and thus are maybe an indication of the degradation of a braided river. In the Opihi, an extremely channelized and degraded river, the average ratio of braided river birds (wrybill, BD, BFT, PS and SIPO) to these river birds in the 4 years of surveys was 1.2. In the Ashley for the past 3 years this ratio has been 4.4, 6.5 and 3.4 respectively. The total of these birds counted this year was 111.

Figure 8 shows the distribution of these birds, with pie charts scaled the same as in the previous maps. Shags (predominantly little shags) and ducks were most abundant near the estuary and in the single channel river for a few kilometres upstream of it. Further upstream paradise ducks predominated. Early this year when the river was drying up, shags, herons and even royal spoonbills were quite abundant further up the river where they were fishing in drying sections of the river.

Other

Twenty-four harriers were counted this year, but it appears that some double counting has occurred as more than one person in each group was counting them – despite instructions for one person per group to do this. Numbers from previous years are unreliable as these birds are generally seen only in the distance. Harriers are a major predator of braided river bird chicks on this river, and perhaps also of eggs. One was captured by a trail camera raiding a BD nest this year.

One Caspian tern was seen east of SH1. No unusual birds, which have occasionally been seen in the past, such as white-winged black tern, were observed.

September 20 2020

Group update

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First of all, apologies for the lack of updates this year. In fact, there have been none, as the last was in December, 2019.

Down on the river

The last season was a good one for bird numbers, as nearly all species were present in record numbers. Breeding results were variable. Up to 10 wrybill pairs nested, raising 8 chicks, and for the first time since 2000 there were two black-billed gull (BBG) colonies containing over 2000 nests. There was also a record number of breeding black-fronted terns (BFT – 111 nests). But fledging results from both species was lower than the long-term average. All the details are in the 2019-20 annual report – due out before the end of this month. The start of this new season has seen the normal variable beginning. All the species are present, although so far only 2 wrybill pairs. The nests of both have been found, but one set of eggs has rather mysteriously disappeared, and the other is in a very vulnerable site. Good numbers of BFT and BBG have been seen, but they have yet to settle on nesting sites. Nests of banded dotterels and oystercatchers have been found, while pied stilts are again in good numbers. But it is still early in the season, so much will change. Once things have settled, we will arrange twilight visits to see the most accessible birds.

Trapping

This is by far our major commitment 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. Rats remain the most common catch, followed by hedgehogs, weasels, stoats and feral cats – with numbers of the last mentioned being greater over winter. For the first time we have been deploying bait stations to try to reduce rats before the breeding season starts, as they were a major issue at the big colonies last season. As were harrier hawks, which we will try to deter using scarecrows. Another source of adult bird losses last season was power line strikes. This season we will seek volunteers to check under lines, so that we have the figures to support an approach to power transmission companies.

Weeds

Weed invasion is arguably our major ‘new’ challenge. Between 2014 and early 2017 there was a significant decline in bird numbers caused by weed invasion and the loss of clear gravel breeding areas, before large floods over the 2017 winter increased clean shingle areas from around 30ha to over 250ha. However, these clear areas are now being reinvaded. As we cannot rely on good floods, around 35 ha was cleared in August by a locally developed tractor-mounted undercutter developed by Cresslands Contracting on Tulls Road. An Iranian PhD student, Sanaz Safavian, continues her studies of weed invasion successions on the riverbed at the Tulls site. Over recent times, the Group has become concerned about management leading to an ever-widening berm zone, which limits ‘room for the river to move’ and leads to loss of the ‘normal’ braided riverbed habitat essential for the long-term survival of riverbed birds. This matter is currently being discussed with ECan.

Human disturbance

The main way to reduce this is by making sure the public are well informed. We do this by all sorts of means, and the annual report’s activity list contains almost 50 entries – mainly articles, interviews, presentations, displays, our website, Facebook page and video. In order to improve awareness further, at the next meeting (see below) we will be proposing the acceptance of a Promotions / Communications strategy, drawn up by professional advocacy member, Steve Attwood. More directly, we annually assist ECan to block off the major vehicle access-ways for the period between September and February . This was completed during August, with signs strategically placed explaining why. Talking signs, a professionally designed interpretation panel will soon appear at the Cones road bridge picnic area.

Finances

The Group’s finances are in good shape. We are now mostly self-funded for our day-to-day existence, with finances coming from a trap making and selling project (197 traps made and 116 sold in 2019-20), donations and sponsorship via Karikaas Natural Dairy Products Ltd cheese sales. Grants for larger special projects, such as the recent 35ha of weed clearing, come from ECan.

Meetings

The COVID situation has allowed us only one general meeting this year – although our 8-person Management Committee has met on five occasions. So, please mark Thursday, October 8 on your calendar for our AGM, followed by a General Meeting. This starts at 7.30pm at the DOC offices on River Road.

As usual, many thanks to all our volunteers for the time taken to support our cause.

– Nick Ledgard, Chairperson

January 21 2020

Survey of the lower part of the Okuku River: November 2019

ashleyriver annual survey, black billed gulls, black-billed gulls, black-fronted tern

The Okuku is an NW to SE running tributary of the Ashley, joining the latter about 22km inland from the coast.

An attempt was made, with Jean Jack of Environment Canterbury, to survey the Grey junction to the junction with the Ashley on 20/10/19, but water levels were too high. On 11/11/19 flow at Fox Creek was only 1.5 cumecs, making river crossings easy.

The survey was done from just below the Grey River bridge on Loburn Whiterock Road to the mouth of the Okuku. Thus the first interval, 8-9 on the below table, was a little longer than a kilometre.

Observations on the survey:

The river has a fairway of up to about 200m width usually with 1 – 2 active channels. A fairly recent sizeable flood seems to have cleared most of the fairway weeds, but some are regrowing.
There were 4 gravel operations seen, 2 large and 2 small. No extraction was currently being done at any of these.
The gravel extraction areas are a definite locus for bird activity and breeding – particularly banded dotterel and pied stilts. Shallow ponds were present at all sites, stilts were seen feeding in these. Extraction areas, shown in yellow in the below map, are approximate only.
There wasn’t evidence of much 4wd activity along most of the riverbed, except for downstream of the Birch Hill bridge. This seems to be a major 4wd access to the Ashley River.
A group of horseriders were seen along the berm of the Ashley just downstream from the Okuku junction, they seemed to be heading out onto a bare gravel island where stilts could be seen.

About 20 cattle were roaming along the eastern berm, and crossing the river to some extent, west of Harpers Road.

Shallow ponds from gravel extraction, Grey River. The title image are shallow ponds, gravel extraction area west of Yaxleys Road.

Bird observations (numbers tabulated below)

Banded dotterel: only seen at and near the gravel extraction area in the Grey River. There were 4 pairs here with 1 almost fledgling chick seen. This is a similar number to that seen on 20 October, the fact that the birds remained there perhaps shows that breeding was successful.

Pied stilt: these were seen at or near all the gravel extraction areas. A total of 20 were seen, with 8 each at the two larger operation areas. One nest was found close to the old extraction area in the Grey and elsewhere the birds’ behaviour indicated nesting.

Black-fronted tern: a total of 12 were seen hawking along the river, sitings near the extraction areas were probably coincidental. The most were seen, 4, just above the Ashley confluence.

SIPO: one was seen at the extraction area north of the Birch Hill Road bridge. This almost certainly had a nest or chicks.

Other: these consisted of typical river birds, including white-faced herons, mallard ducks, Canada geese and little shags. They were distributed along most of the river.

January 21 2020

Lees Valley – Okuku and Ashley-Rakahuri Rivers: 2019 Breeding Season

ashleyriver annual survey, black billed gulls, black-billed gulls, black-fronted tern

Introduction

The Okuku is a NW to SE running tributary of the Ashley, joining the latter about 22km inland from the coast. It rises in the Pancake Range north of Lees Valley, runs through this valley and enters the Okuku Gorge. The section through the valley is about 3km long, here the river is relatively wide. The gorge section is about 10km long and is quite narrow. From the south end of the gorge the river runs for about 15km to the Ashley confluence.

The Ashley rises in the Puketeraki and Pancake Ranges and upper branches of it run for a considerably greater distance through the flat Lees Valley.

On October 20 2019 Jean Jack of Environment Canterbury surveyed river birds on short sections of the Ashley and Okuku Rivers in Lees Valley in response to proposed gravel extraction. The 700m Ashley section was just downstream from a bridge some 10km northeast of the Ashley Gorge. In this area black-fronted terns (BFT), banded dotterels (BD) and pied oystercatchers (SIPO) were displaying breeding behaviour – but no nests were found. Three kilometres of the Okuku River was surveyed either side of the Lees Valley Road crossing. Birds found here included BD, BFT, southern black-backed gull (SBBG), SIPO, black-billed gull (BBG) and pied stilt (PS) – most displaying breeding behaviour. A colony of 25 BFT was identified, although nests were not found. A black-billed gull colony was found just below the Lees Valley Road river crossing, at that stage only 8 birds were present.

BRaid activities

The evidence of braided river birds breeding in the Lees Valley was thought by BRaid to be worthy of further monitoring. On 21/11/19 the Ashley and Okuku sites were visited by Grant Davey and Howard Esler. Further visits were made to the Okuku site on 19/12/19 and 14/1/20 by Grant Davey and Nick Ledgard.

Ashley River

Birds were counted along 1.4km of the riverbed downstream from the upper Lees Valley bridge. These included 8 BDO, 7 BFT, 6 SIPO and 4 PS – constituting a large population of birds in such a short section of narrow riverbed. Several terns were resting on the ground, but their behaviour did not suggest the presence of eggs or chicks. They may perhaps have had nests but lost them to predators. Four juvenile BDO were seen, 1 in flight – they seem to have had a successful nesting season. SIPO behaviour suggested the presence of 3 nests and stilt behaviour suggested 2 nests.

The area traversed was within and just downstream from where gravel has been extracted in recent times. Gravel extractors have probably created favourable nesting habitat.

Okuku River

When visited on 21 November the 2.5km of riverbed traversed from just below the road crossing to 2.5km above also had a very high concentration of braided river birds for such a small river. These are illustrated and tabulated below:

The BDOs were mainly in pairs and appeared to have finished nesting, however only 1 flying juvenile was seen. Most of the SBBG were resting on the ground close to tern colonies. Stilts were breeding in the area and 1 nest was found. The SIPO did not display obvious breeding behaviour.

Fourteen BFT nests were found – 2 were empty, 1 had a dead chick and a live chick in it, 1 had a single egg, the remainder had 2 eggs. No concerted effort was made to find nests, but they were quite easily located – those found would likely have been more than half the total present. Three clusters of nests were found – about 0.6, 1.4 and 1.5km upstream from the road crossing with 3, 9 and 2 nests respectively. The nests were on weed-free islands up to about 15m in width.

Black-fronted tern colony, looking downstream.

The previously observed BBG colony had expanded to 292 gulls – counted from a drone image. Chicks had yet to hatch. This colony was in coarse gravel on an island (see the image at the top of this post taken 29 November, looking toward Okuku Gorge).

The visit on 19 December was specifically made to monitor the tern and gull colonies. On this date there was no activity at the lower and upper BFT colonies, but at least 6 juvenile terns were seen at the middle and largest colony. Three were flying, another appeared to have a broken wing and 1 was yet to reach fledgling stage. The chicks were observed from the riverbank to minimize disturbance and it seemed likely there could be more than were counted.

On 19 December the wind was too strong to fly the drone, but the BBG could be counted quite accurately (198) off photographs taken from the adjacent high bank. The reduction in adult numbers since 21 November was in line with experience from colonies on the Ashley River (this happens while nest and chick numbers remain largely the same – non-breeding adults leave the colony and breeding adults spend more time away foraging). Most eggs appeared to have hatched with chicks ranging from recently hatched to perhaps about 2 weeks old.

Pair of BBG chicks being fed, other gulls still on nests, 19 December 2019.

Discussion

In November braided river bird numbers were high on the short sections of the Ashley and Okuku Rivers that were traversed by ECan and BRaid. On the Ashley these numbers were likely boosted by the positive influence of gravel extraction. The following points are specific to the Okuku River:

The black-billed gull colony appears to have been successful. Chicks were hatched and from the lack of predation evidence and low number of dead chicks in the colony area, many were likely fledged.

The black-fronted terns appear to have had some fledgling success, probably higher than that of those on the lower Ashley in 2019 – 2020.

Ground predator numbers in the area seem low – no sign of predation was seen around the gull colony and the landowner/manager (Craig Thompson) reports having seen very few predators in his time on the property. Rabbits were common, this could perhaps lead to more predators in the future.
Black-backed gulls are plentiful in the area, much more so than along the Ashley River. However, there was no evidence seen of them being active predators of braided river birds. Harrier numbers also seemed high.
The area has notably few invasive weeds. The banks have mainly grass and matagouri with in places a number of native species present. The most obvious weed is Vipers Bugloss.
Larks (pipit/skylark?) were abundant in the area.
The contribution to braided river bird nesting success of such small out of the way rivers is probably underestimated. It is planned to revisit the Lees Valley next nesting season and to survey the Okuku for some kilometres upstream from where it enters the gorge. There could have been other nesting colonies upstream of those observed this year – the landowner mentioned that he may have seen more nesting terns higher up.

– Grant Davey

December 13 2019

Ashley-Rakahuri Rivercare Group update

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Down on the river – bird numbers. Without doubt, the highlight of the last few weeks has been our annual bird survey on November 16. The Group’s mission is to improve the lot of the native birds which annually return to breed on our river, and our once-a-year surveys are the only chance to find out if we are achieving this goal. So, it was most rewarding to see 29 volunteers gathered on a fine (if windy) Saturday morning to get their survey instructions. The river flow was such that crossings were challenging, but certainly do-able, so that everyone completed their stretch and were off the river by midday. Needless to say, the survey sheets were quickly gathered and analysed, revealing that numbers for all species were the highest since we began in 2000 (see bar graph below). We saw 27 wrybill, 6 more than ever before. Thanks to there being two colonies this season, numbers of black-billed gulls (BBGs) were many-fold higher than before (over 4000). However, they are not included in the graph, as the presence or absence of a single colony, can have an over-riding influence when comparing total bird numbers from one year to the next. We reckon that the increase is mostly due to greater areas of clean shingle (less weed presence) since when bird numbers started to decline after 2014. Plus the fact that other adjacent alpine-fed rivers (such as the Waimakariri) were in full flood, forcing birds which usually occupy them to look elsewhere. This is almost certainly the case for black-billed gulls. A new species for a survey was the black-fronted dotterel (4 of them, and almost certainly breeding); a species which has been steadily increasing its range south over recent years.

Down on the river – breeding success. Determining bird populations is much easier than recording breeding success, particularly if one is trying to determine the influencing forces. This requires constant monitoring of adults and chicks, the latter often being very hard to detect. We only monitor details for wrybills, black-fronted terns (BFTs) and black-billed gulls (BBGs). At least 8 wrybill pairs took up territories, with nests found in 5. Fledged chicks have been seen in 3 of these. Four BFT colonies were located (involving possibly 80 pairs), but no chicks have yet fledged. As mentioned above, the biggest breeding increase has been with BBGs, with two large colonies (Railway and Toppings) which have numbered well over 4000 birds. The number of nests is hard to determine accurately until the sites are vacated, but it would be 1500+. Chicks are in the process of hatching, and some are just reaching the age at which they gather together in creches. It appears that some BBGs are still just arriving (late refugees from other flooded rivers?), so the fledging period may be more drawn out than usual. Good numbers of breeding pairs of other species (pied stilts, banded dotterels and S. Is pied oystercatchers) are also present on the river.

Trapping. Grant Davey sends our 27 trappers excellent monthly summaries concerning predator trapping results. Even though individual trappers may be currently experiencing a low catch rate, the overall figures for this year show that we are making an impact. Since February 1 this year, we have caught 411 predators alongside the riverbed – with rats and hedgehogs being No 1 (112 and 111), followed by weasels (77), feral cats (37) and stoats (24). Out around the estuary, the catch figures are quite different. Since we started in late June last year 344 predators were caught – with rats being at the top (168), followed by weasels (91), stoats (34), feral cats (14), hedgehogs (8) and ferrets (7). In addition to this trapping effort extending over 21 km, we have been doing more intense grid trapping around the BBG and BFT colonies – using 53 specially made, lightweight and cheaper run-through corflute tunnels, housing DOC 150 traps. The main target is Norway rats which appear to be escaping attention by living in mid-river debris piles – as they are not being caught in the berm zone where virtually all of our other traps are located. Rats can be devastating on BFTs at the egg-nest stage, and were probably responsible for the loss of 20 BFT nests at the Railway site before the offenders were trapped. Interestingly, BBGs nesting right alongside were not troubled, almost certainly because rats will not take on aggressive gulls nesting in close proximity to each other.

Weeds. As mentioned in the October Update, before the season started we cleared weeds from a number of hectares using a specially created tractor-mounted ‘undercutter/ripper’. The Railway BBG/BFT colony is occupying one of those sites. And as indicated above, the record numbers of birds counted this season, could well be responding to greater areas of clear, weed-free shingle than there was from 2014-2017. However, the threat of weed invasion is as great as ever – well indicated by the dominant lupins, which are currently flowering and colouring much of the riverbed yellow. Not so obvious are other weeds such as broom, gorse and blackberry and the equally frequent younger lupins which have yet to flower. Unless a major flood occurs before next season, or we step up our weed control efforts, then bird numbers could well decline again as the clear shingle areas become invaded. A recent inspection of the smaller foothills-fed rivers in S. Canterbury (such as the Opihi and Orari) amply reinforces this ‘beware of weeds’ message.

Human disturbance. After predators and weed invasion, the biggest threat to the future of the birds is disturbance by humans. Our awareness efforts, coupled with good signage and the physical blocking of 4WD access ways during the breeding season, means that disturbance by people and their machines is way less than it used to be. To be sure, there will always be the small percentage of people who wreck signs and go out of their way to get onto the riverbed, but there is little that we can do about them. At many of our meetings, there is vigorous discussion as to how best to increase public awareness, as it is often difficult to determine the relative cost-benefit of expenditure in this area. To this end, the Group recently formed a promotions sub-committee to work on a strategy which allows us to better plan our public awareness efforts.

The future. There is little doubt that the Group’s many years of management, primarily aimed at controlling predators, reducing human disturbance and removing weeds, has contributed to the present buoyant situation for the birds on our local river. It is equally accurate to say that we will have to continue this effort to maintain a positive situation – probably even increase it relative to weed control. In this respect, we are fortunate that over the last couple of years ECan has prioritised a step-change in its indigenous biodiversity efforts, and agreed that braided rivers be identified as a priority area for increased attention. A commitment was made to produce nine braided river plans over 10 years to 2028, and the Ashley-Rakahuri river was chosen to be one the first cabs off the rank. We are having discussions as to the form this might take, but the result should be an improved ability to ensure a better future for our local braided river birds.

Many thanks to all our volunteers for the time taken to support our cause.

Nick Ledgard

Chair, Ashley-Rakahuri Rivercare Group Inc

November 24 2019

Annual survey (Nov 16, 2019) results

ashleyriver annual survey

The first Ashley-Rakahuri Rivercare Group bird survey was in 2000, so this was our 20^th consecutive such event. It attracted the most volunteers ever (29), and it was pleasing to note that for a good number of them it was their first braided river bird survey. The weather was fine, if a little windy at times, and the river flows were average, making for some interesting but safe crossings. Volunteers were divided into four groups to cover the 20km of riverbed, starting at the Okuku junction and finishing at the SH1 bridge. All people were off the river by midday. Later on a small group surveyed between SH1 and the estuary.

So what was the outcome? The major focus is on six species – the wrybill (ngutupare), black-fronted tern (tarapiroe), black-billed gull (tarapuka), banded dotterel (pohowera), pied stilt (poaka) and the S. Island pied oystercatcher (torea). Those of us who had walked the river prior to the survey suspected that bird numbers would be up. And we were right – much more so than we expected. The numbers of all species were records within the period since we started in 2000. The total number of birds of each species counted between the Okuku junction and SH1 was 5,350. This number was considerably boosted by there being two large colonies of black-billed gulls – a total of 4,097 mainly counted from drone photographs. In the past, there has never been more than one such colony, and for over half of our surveys there have been no colonies present at all.

The reason for the high numbers is likely to be largely due to the riverbed being relatively free of weeds, plus regular floods in the Waimakariri River may have forced some species to relocate (almost certainly the case for the black-billed gulls). It is also reasonable to assume that the Group can claim credit for its many years of management, primarily aimed at controlling predators, reducing human disturbance and removing weeds.

Many thanks to survey organiser, Bev Alexander, and all those who assisted on November 16.

A full report on the survey will be completed in the near future – during which all numbers will be thoroughly re-checked. Grant Davey has presented our survey results in the attached figures.