NZ DOTTERELS

NZ DOTTERELS ON AUCKLAND’S WEST COAST by Adrian Riegen

Since the 1980s I have been monitoring New Zealand Dotterels (NZD) and Variable Oystercatchers on Auckland’s west coast, in particular on Karekare Beach. For many years the populations have remained low but stable with usually two to three pairs of each species in the Whatipu Scientific Reserve from Paratahi Island south to Pararaha Stream. The other main beaches, Piha, Anawhata and Bethells (Te Henga) have had very low numbers of both species and even less success at raising young than at Karekare. Was this due to human disturbance and predation or some other factors such as the harshness of the west coast weather and hot black sand, compared to Auckland east coast beaches, where in spite of much greater human induced pressure more New Zealand Dotterels were raised.

This is without doubt helped considerably by community groups set up along so many beaches, putting fences round nesting birds and undertaking predator control and educating the public. Now Bethells, Piha, Anawhata and Karekare have community groups led by some wonderfully dedicated people to help protect these birds.

In spite all this the west coast populations of NZD have barely increased, even when they do fledge young birds, so what is happening to those young birds? Are they dying soon after fledging or leaving the west coast permanently to find a less wild place to live?

And are any raised on the west coast recruited as adults to nest there?

To find out what happens to them we are attaching a metal band and an engraved flag to the legs of young birds, so individual birds can be monitored. Unique numbered metal bands should last the life of the bird, which can be as much as twenty plus years.

However, the numbers on the bands are so tiny that they are almost impossible to read. Even with good optical gear and so rely on the bird being recaptured or found dead to learn anything about them.

We have other options to track individual birds and the simplest and cheapest is to also fit them with a small engraved ‘flag’. This is in fact a plastic ring with a tag that sticks out, hence the flag (See photo). There is a protocol for using flags and like the metal bands this is approved by the Department of Conservation (DOC) through their bird-banding scheme. Anyone using bands and flags must have a banding license issued by DOC and a permit to carry out the project.

I have been banding migratory waders in New Zealand since the mid 1980s and the information gathered over the decades has helped us understand the migration routes of Bar-tailed Godwits and Red Knots and longevity of the endemic Wrybill.

On 10 January 2018, I fitted the first engraved flag, CLH to an NZD at Piha.

All the flags are white with three black letters. These are easier to read than the metal band either with binoculars or with the help of a camera. The flag means individual birds can be tracked without disturbing them or the need to recapture them for years to come.

We are still seeing some godwits with flags that were attached in 2008.

From modest beginnings in 2018 what have we learnt about young birds raised on the west coast? Some adults are also caught and they get a flag as well.

Projects like this take years to gather enough meaningful data to understand what birds are doing but with each passing year, and thanks to observers passing on their sightings we can build a picture of what is happening. This is a good point to remind people that each, ‘Sighting of a tagged bird will be of interest to someone somewhere’ as a woman on a remote Alaskan island thought when she saw a godwit with a white flag. A few emails to people she thought might know about it, brought it to my email inbox and minutes later she had all the information about that bird, when it was banded, where it had also been seen and its minimum age. Every observation helps build the picture even if it’s from the beach where it was banded. We have had instances where an individual has been seen on two or more west coast beaches on the same day, so although they may appear to be residents they may be moving up and down the west coast on a regular basis. To date at least 42 people have reported flag sightings and each and every one is a valuable contribution to our understanding of these special birds, so a big thank you to them all. It should also be noted that just because birds are not seen it doesn’t necessarily mean they are dead. They may just be at beaches not regularly visited or just eluding observers.

Back to the facts and what we have learnt so far. This research will continue for some years to build a better understanding of NZD movements on Auckland’s west coast.

Of the 50 young birds banded and flagged, 37 have been seen at least once since fledging. We normally band the young birds at about four weeks old, as they have a better chance of surviving from that age. They can usually fly at least short distances at about five weeks old.

Summary

We have put engraved flags on 5 adults and 50 chicks on the west coast from Bethells to Karekare since 2018, with two adults banded at Piha, two at Karekare and one at Bethells. Of the chicks 22 were banded at Karekare, between 2018-2024, 14 at Piha 2018-2023, 7 at Anawhata 2019-2024, 4 at Bethells 2021-2022 and 3 at Wigmore Bay 2022-2023. Of the 55 birds flagged, 37 have been seen at least once somewhere, with CHR seen the most, 101 times.

Where have they been seen?

Auckland’s West Coast

Of the 50 chicks banded on the west coast beaches seven have been seen at Port Waikato mostly during autumn and winter and two a little further north at a Kariotahi Beach. A further Nine birds have been seen at sites on the southern Manukau Harbour. One bird, CHT, banded Piha February 2019 is now resident at Big Bay, Awhitu Peninsula and is breeding there. One has been seen at Whatipu. Two have been seen briefly at Muriwai. I was expecting many of the birds to join the autumn non-breeding flocks in the Kaipara Harbour but only one has been seen there, that was CHR. More on that one later.

JAJ, banded Karekare December 2021 was seen in March and June 2022 at Clarks Bay, South Manukau Harbour. It was then seen on Te Motu in Kawhia Harbour in July 2023. Perhaps it has settled there now. Te Motu is rarely visited by birders.

Auckland’s East Coast

Five have been seen on the east coast of the Auckland region. CLH, banded at Piha in January 2018, was seen at Shoal Bay, Waitemata Harbour in April 2018 and then from January to September 2019 at Whitford, east Auckland but not seen since then. CNU, banded at Piha in December 2020 was seen at Omaha between February and August 2021. Many non-breeding NZD gather in autumn at Omaha before dispersing again to breeding sites. Most interesting are the three birds that have been seen between Kaiaua and Pūkorokoro Miranda on the Firth of Thames, a distance of at least 80km. JAB banded at Piha as a chick in December 2021 was seen on the Firth of Thames in June 2023 and then back at Karekare in January 2024.

Which chicks now breed on the west coast?

Of the 37 chicks banded on the west coast beaches since 2018, only two have been recruited to the west coast breeding population. Hopefully more will be recruited in the coming years. They generally do not breed until at least two years old. The two recruited are: CHR, banded at Piha February 2019 and has been seen over 100 times, only in the scientific reserve part of Karekare beach. It has bred there each year since 2021 and two of its chicks, JAW and JAX, were banded in February 2023. CNZ banded at Karekare February 2021 and seen there until March 2021 then seen at North Piha regularly since July 2022 and has been breeding with HAB since then.

Also of interest is the fact that 95 NZD have been banded and fitted with flags at other sites around Auckland since 2011 and not one has been seen on the west coast as yet.

A big thank you to everyone helping to protect the dotterels and for submitting sightings.

Hopefully the story will continue next summer!

Adrian Riegen March 2024