Braided River bird breeding across the SI and human disturbance
Top image: Ashburton Hakatere hāpua and river mouth (courtesy Andrew Crossland)
Complied by Frances Schmechel (ECan), the following reports briefly outline the impacts (not all negative) of human disturbance on bird breeding colonies on several South Island rivers over the 2021-2022 season.
Ashburton Hakatere River
– Donna Field, ECan: 2/5/22
The main area I observe birds is the Ashburton River at SH1 and the river mouth.
There was a colony of black-billed gulls under SH1 bridge that fledged around 100 chicks.
Although major repair work was going on at the bridge the contractors did a great job of minimal disturbance of the birds and actually in the end the breeding was successful as the gulls shifted onto the high bund that was protected from floods, to nest after being flooded out 3 times previously.
The largest human disturbance I have noted of birds is on the shags and dotterels on the shingle spit of the hāpua and on the mud flats of the hāpua (top image). Motor bikes and 4-wheel drives use the spit to access the mud flats to ride on and to go to the mouth for fishing. People also let their dogs run free in this area. This normally causes a complete lift of the shags and or a rising of the dotterels off their nests.
Exacerbating this issue will be the up-and-coming formation of a motorbike park by Ashburton District Council in the donga adjacent to the spit and increased number of motor bikes in the area.
Editor’s note: multiple signs located strategically inform people of the area’s significance:
Clarence River Mouth and Charwell River (Conway Catchment)
– Heath Melville, ECan: 1/5/22
The Clarence rivermouth had an abysmal season for red and black-billed gulls, and white-fronted terns. Initially being washed out by big seas, a second breeding colony formed just before Christmas with numerous human impacts.
Against the odds, there were upwards of 90 chicks present around January, with 60 plus nearing fledging in early February. Flooding in February seemed to wash away the almost-fledglings, which were initially given an island, from the awa (river) cutting through the shingle spit.
After the colony was abandoned and presumably no chicks fledged, I surveyed the hāpua and found a couple of gulls and a small colony of approximately 40 mostly juvenile white-fronted terns. I believe these may be fledglings from this colony.
Not sure how the black-billed colony got on in the Charwell River (Conway catchment). A colony of Southern black-backed gulls formed next to it. I’m hopeful we can conduct predator control and basic monitoring here this coming season, as it has historically performed very well with limited intervention.
Mouth of the Waiautoa/Clarence and Marlborough
– Patrick Crowe, DOC: 2/5/22
As Heath mentioned, the mouth of the Waiautoa/Clarence river was particularly bad this year for human-related disturbances but the birds there still did manage to fledge some chicks despite all odds. As you are well aware the black-fronted terns in the upper reaches of the Waiautoa bred quite successfully this season. Molesworth Station had a lot of people going through especially over the summer period and there was plenty of misbehaving but this seemed to be more directed at huts, tracks and signs than at the wildlife.
For Marlborough unfortunately I didn’t get a chance to get out on to the Wairau or Awatere Rivers to see how the colonies went but I did seen relatively good numbers of fledged black-billed gulls and black-fronted terns out at coastal locations such as the Wairau Lagoons following the breeding season.
Birds breeding on Marlborough rivers probably faced the same pressures as usual from 4WDs, jet boats, dogs, predators and people but fortunately had no major spring or summer floods to further impact their breeding success.
– Grant Davey, ARRG: 29/4/22
I think this season was good on the Ashley as far as disturbance goes – due to blocks being put in, education and publicity. The publicizing of 4wds and motorbikes in a black-billed gull (BBG) colony the previous season probably did some good. I found several 4wd and motorbike tracks through black-fronted tern (BFT) colonies (only saw it happen once), but no nests were run over and I saw no evidence that birds had been frightened off nests for good. Two banded dotterel (BD) nests that we know of were run over and 2 wrybills had very close calls.
The only BBG colony was the one at the estuary, which we didn’t have time to monitor properly. This seemed an impossible situation, with whitebaiter vehicles all around. ECan put up some signs, but they are of debatable use as they inevitably get driven over. Despite this, there were hundreds of fledglings produced. There were also two BFT colonies of about half a dozen nests each nearby. One of these got badly driven through and the total fledglings that I saw was 2.
We found 107 BFT nests between the Okuku and SH1 – our main area. These produced 13 fledglings that we know of. This was due mainly to Norway rats and flooding. If the early colonies hadn’t been wiped out by rats, there would have been no need to make the nests that got flooded out later on.
Despite the efforts of DOC, some latecomer 4wds deliberately went through 3 BFT colonies on crate day – between the gorge and the Okuku, which is really out of our remit. But no nests were run over and the birds weren’t frightened away. The largest of these colonies produced about 7 fledglings from around a dozen nests. One colony got washed out, the other I think was wiped out by predators.
– Courtney Bamber, ECan: 27/1/22
We spotted some black-bills at Woodstock on an aerial survey of the Waimakariri to count Karoro. Woodstock is an isolated area of shingle at the bottom of the Waimakariri gorge with only one access in and out. It’s popular with jet boaters and kayakers as a launching point.
I went to the site a couple of days later and it was immediately apparent there were also a significant number of black-fronted terns present, as well as wrybill (image below). There were tire tracks through the tern colony to a jet boat launching point.
I put up signs and painted a dazzle line on the ground to effectively split the shingle Woodstock area in half. People would still have room to park and launch boats at the northern end of the site. I rang the head of Jet Boating NZ – Canterbury Branch and asked him to put a message out to their members, which he agreed to. There were also a number of other social media posts about the site (including via our own channels) that reached a large number of people.
Canterbury anniversary weekend was coming up so I put a note out to Braid and ARRG asking if they had any members keen to volunteer to sit up at the site over the long weekend and talk to people visiting the site about the birds. I had 4 people come back to volunteer.
Our ornithologist (Niall Mugan) visited the site and put traps along the adjacent bush edge. Niall also was the point of contact with the volunteers over the long weekend. The volunteers took turns sitting at the entrance to the shingle fan and talking to people accessing the site about the birds. They reported that most people actually already knew about the birds from social media and were good about it. All in all, a reasonable success.
A few days later there was a moderate fresh through the river. We watched the water rising through an Outdoor Access livestream camera at the gorge, but the black-bills and most of the terns survived the peak of the flood.
Two days later I checked the Outdoor Access camera again and all birds were gone. Niall subsequently visited the site and confirmed all birds had gone and that there were three dead black-bills on site. He met one of the volunteers up there who had also gone to check the birds, and she took photos of the dead ones which she sent to the media.
We believe it was a dog as the dead birds were found quite a distance from the original colony location and hadn’t been eaten, but had been thrown around and played with, with multiple broken bones. A dog running through the colonies disturbing birds would also explain the collapse of the entire colonies. There was also a campfire nearby with a 100+ year old beach tree cut down and set on fire. We believe people camped on site and had a dog with them.
I’m not sure what I would have done differently. It would be impossible/unsafe to permanently have people up there (flood-risk, amongst other things). The water was still quite high at the time so I didn’t even consider people would camp there.
Since then, we have had another large group of black-bills set up behind McLeans Island, further down the river. There are also heaps of banded dotterels plus a number of black-fronted terns. Can’t say for certain that it’s the same group of black-bills, but they did turn up shortly after the collapse of the Woodstock colony.
Positive learnings –
- The volunteers were great and really effective out on site. This is something to build on in future.
- The media coverage was quite massive and heaps of people heard about it, so that was a win.
- The disturbance was at least early enough in the season that the black-bills had time to re-nest elsewhere (although would have spent some energy by this point).
– Clement Lagrue, DOC: 29/4/22