Artificial nesting platform for tara / white-fronted tern in an urban estuary


Tarāpunga / red-billed gulls (Chroicocephalus novaehollandiae scopulinus) and tara / white-fronted tern (Sterna striata) nest on artificial structures in the Tāmaki Estuary, Auckland, New Zealand. The Department of Conservation ranks both species as At Risk / Declining (Robertson et al. 2021). Both species have also nested on moored boats in the estuary which creates human-wildlife conflict.

Piles under Waipuna Bridge (middle, photo taken from land). Photo by Shaun Lee.
Piles under Waipuna Bridge (western end, photo taken at low tide). Photo by Shaun Lee.


A nesting platform on the large piles (72cm diameter) that rise c2m above Mean High Water Springs (MHWS) under Waipuna Bridge. The piles are safe form mammalian predators who could not swim then climb to the nests. This area is less impacted by light pollution than Panmure Bridge where there is a tarāpunga colony.

The nests are exposed to avian predators including the adjacent tarāpunga.Using vertical canes to stop flying attacks on chicks. See Preston Dock Common Terns below.  
The nest structures might be used by tarāpunga.This is not a poor outcome but if the spaces are deep and small they might not be so suitable for tarāpunga. There is a small chance that nearby nesting feral pigeons are also interested in the structure.
Colonies are ephemeral (McLean 2018) with birds moving regularly.This could be an advantage as species with higher site fidelity would be harder to attract. Suggest the addition of a 3D printed decoy to improve the chances of success I the first season.
The structure will attract human attention.Clearly label the structure as a ‘trial bird nest for endangered terns’ include a phone number & URL to a blog post about the project. Centre the decoy to keep it less accessible / visible to humans. The height of the piles will help deter vandals. Even at low tide access requires a boat or a swim. Graffiti on the bridge may have been enabled by retired pontoons.
Installation difficultiesThe piles are tall and using a ladder on a boat is tricky. A platform that connects the piles is visible 2.5hrs after high tide at the western end. A ladder could be used on the platform but it will be slippery.
MonitoringThere is no pedestrian access to the bridge. A land based site inspection from Finn Place identified the western piles as easy to monitor.
Preston Dock Common Tern nest boxes made by the Fylde Bird Club in Lancashire.

Tara do not use nesting material (NZBirdsOnline), a small amount of sand could cover the floor of the nests. The Preston Tern Nest Boxes use gravel. Drainage holes should be added to keep water out.

Proposed design

Based on the Preston Dock Common Tern nest boxes. Tara are not much larger than Common Tern but we have made the nest boxes smaller to dissuade  tarāpunga form nesting here. Boxes dimensions made of ‘Radiata Premium Grade Smooth Decking 140 x 32mm’. The extra depth allows for a max of 40mm of gravel.

How the nest boxes might attach to a platform on top of the piles.


Tara tend to arrive at a prospective nesting location only a few days before laying, and there is a high degree of synchronisation of laying within a colony (NZBirdsOnline 2022). Eggs are laid between October-December (NZBirdsOnline 2022). Prospecting may begin weeks before egg laying. We plan to deploy the structure by mid September.


The structure was deployed on the 14th of September 2022 (with a few modifications). I had a huge amount of help from a friend who is much more handy with an impact driver than me. The decoy is a bit odd looking as its just a scaled up tara iti with a different paint job. Five tara flew past while we were working and roosted on the piles in the center of the channel. We decided not to deploy the canes until we had active nests.

Update 15 Sep 2022. 10:00am-10:45am.

Four tara and three tarāpunga were roosting on the piles in the centre of the estuary. Every ten minutes or so they would be quite loud with both species calling and jostling for space but no confrontations observed. There were three close passes of the decoy and on at least two of these occasions it seemed like the terns were calling at it. No terns landed on the boxes but both species visited the piles near me. One tern was foraging from a pole which gave it a good view of any fish swimming above the platform in the shadow of the bridge, but it did not dive. One tern dived on in the centre area.

Update 18 Sep 2022. 5:15pm-6pm

About three gulls regularly on the piles in the centre of the estuary. Lots of gull movement and calls, more gull activity between the bridges than the 15th. No terns seen.

Update 28 Sep 2022. 2:15-2:20pm

Constant red-billed gull activity. Three gulls roosting on centre piles. Two pied shags feeding on the southern side.

Update 10 Oct 2022. 1:00-1:01pm

Low tide, no activity. Just a pied shag foraging under the bridge.

Update 23 Oct 2022. 5:00-5:01pm

High tide, no activity. Just a few gulls roosting on centre piles.

Update 02 Nov 2022. 1pm.

Photo taken from pole mounted GoPro shows gulls are prospecting the nest boxes.

A pair of tara have nested on one of the center piles.

Update 26 Nov 2022. 11am.

Two pairs of tarāpunga have nested in the boxes. One of them has really filled it up with material!
Tara also look to be nesting in an adjacent boat.

Update 23 Dec 2022. 12pm

The first pair of gulls have a chick, the second nesting gulls have not increased their nest height at all. Maybe because the other pair can keep watch.

Update 15 Jan 2023. 5:30pm

I’m hoping the chick is in one of the nest boxes and the second nest is not being sat on because it is hot, and the nest has a chick. Alternatively there is another adult down in the nest box. If the recent storms had destroyed either nest or pushed the chick off the adults would likely have moved on.

Update 18 Feb 2023. 5:00pm

The structure is cyclone proof! Weather stations at St Helier’s and Howick recorded wind speeds of 40 knots (74kph). Despite the roosting gulls in the photo I dont think there were any active nests on the structure today.
Additional visit 22 Feb shows nesting material in five of the six boxes. To my knowledge only the two with the most nesting material were used for nesting.

Update 22 Nov 2023. 11:00am

The gulls nested here earlier this year with a chick ready to fledge already. It also looks like at least three of the nest boxes were utilised. There was also a juvenile on a nearby boat and on a pylon under the bridge where tara nested last year.

Update 28 Jan 2024. 2:00pm

The gulls are still using the platform for nesting even tho there is space at the main colony. I think the design is just too appealing to gulls.


NZBirdsOnline 2022. Accessed August 2022.

Robertson et al. 2021. Hugh A. Robertson, Karen A. Baird, Graeme P. Elliott, Rodney A. Hitchmough, Nikki J. McArthur, Troy Makan, Colin M. Miskelly, Colin. J. O’Donnell, Paul M. Sagar, R. Paul Scofield, Graeme A. Taylor and Pascale Michel. Conservation status of birds in Aotearoa New Zealand, 2021. New Zealand Threat Classification Series 36. Department of Conservation, Wellington. 43 p.

Mclean 2018. Successful restoration of an unnatural breeding habitat for white-fronted terns (Sterna striata). Notornis, 2018, Vol. 65: 54-58. The Ornithological Society of New Zealand Inc.

Replica Tūturiwhatu  / Northern New Zealand Dotterel

It was a joy to work on these tūturiwhatu which were a gift to Alison Stanes QSM for her work at the Tāwharanui Open Sanctuary Society Incorporated. Alison taught me a lot when I began minding dotterel. Sharon Kast and Sally Richardson did a great job of banding the models and adding a shell base.

Photo by Sally Richardson

A fish decoy for my camera

I do wide angle macro photography underwater which helps me take great photos in yuck conditions. However it’s not so good for bigger fish who tend to not get that close. I tried 3D printing a little decoy for the end of my camera to see if it changed fish behaviour.

3D printed fish decoy that uses the laowa probe lens as an eye

I have only used it once but so far:

  • Bigeye (which the decoy design was based on, were not even a little interested).
  • Triplefins are not longer swimming under my lens (thats useful) but might be a bit more timid.
  • Red moki seem really curious, I’m sure they are doing a ‘double take’.

I’ll adjust my decoy a bit and do some more tests.

Fooling flamingos

I have been helping out Auckland Zoo and the Department of Conservation with important conservation work, and last year Auckland Zoo had an unusual request.

 “Can you make flamingo eggs? Our flock of Greater flamingos have a tendency to kick their eggs into the water, so we give them a ‘dummy’ egg whilst we place their precious egg safely in an incubator.”

In the past I have only assisted with endemic or threatened species so I was a little hesitant, that was until I went on a short tour of the Zoo’s flamingo habitat and met the birds. I learnt that in the wild, flamingo habitat is indeed threatened, and I was captivated by these elegant, head-high birds. One of the young females named ‘Otis’ wandered over and gave me a friendly chest bump. Immediately smitten, I  have made 21 eggs for the flock. There were two technical challenges:

  1. The eggs have an unusually rough surface, I started off covering the smooth 3D printed models with epoxy but this quickly became laborious. Instead, I sculpted a texture on the 3D model and was impressed how well it printed.
  2. I had to get the weight just right. I achieved this by filling the eggs with sterilised sand, then water to make sure pressure changes from expanding and contracting air bubbles would not stress the resin shells.

One of the eggs has been successfully tested and I hope Otis & co will be happier spending more time sitting on eggs.

Fairy tern models used as stand in parents

New Zealand Fairy Tern at Auckland Zoo

In December 2020 I jumped at the chance to help the Department of Conservation and Auckland Zoo with New Zealand’s most endangered bird. I provided 3D printed fairy tern models (that were designed for use as decoys) to Zoo staff who hand reared a chick through to fledging. A soft yellow tape was wrapped around the models beaks to make sure the valuable chick did not injure itself. The models stayed with the chick to its aviary bach until it learnt to fly and feed for itself.

Artificial shag roost

This artificial shag roost in Hobson Bay was constructed by Auckland Council to mitigate the effects of a boardwalk being constructed next to an existing shag roost. Nesting materials and a plywood decoy has been added but the birds are yet to show interest in it.

Red-billed gull decoys

I was recently asked to quickly create some red-billed gull decoys. I joked they might be better of using a decoy picnicker but the reality is this is another native species that is in real trouble (conservation status declining). I posed the decoys with their tails up but with legs so they could be used standing or sitting if they need extra anchorage.

Unfortunately these decoys were snapped off at the leg, we are not sure how, as it would involve a lot of force. So…

I made some more, these have been redesign to bolt on to a 1M long 8mm diameter threaded rod.
Here is what they look like installed. We dug holes in the ground and used a little cement to lock them into place. Fingers crossed they work.
Photo by Paul Kennedy
Photo by Tim Lovegrove.

Update October 2019: Win!
Note that the Northland Region Corrections Facility is making wooden Black-billed Gull nesting decoys, I don’t know how much they cost but they look cute!

A great article on the Wynyard gull colony project has been published here. Another one by Boffa Miskell. Ohhhh and another article in the Guardian!

3D printing replicas for a museum

This was my most challenging project for 2018. After reading about the New Zealand Fairy Tern decoys I was making, the Mangawhai Museum approached me to make them some replicas. As there are only 40 of these birds left in the world they were never going to be able to get a taxidermy one for an exhibition.

I was very ambitious and decided to create a feeding scene where the male is landing with a fish in his bill. This was very challenging and I really pushed my printer to the limits and discovered a few new tricks in the process. I think this kind of model making has advantages over taxidermy where the models can be designed to exhibit a wide range of behaviours. It will be interesting to hear how the public react.

Australian fairy tern decoys

After talking about my New Zealand fairy tern decoys I was approached by Australian conservationists about making decoys to attract Australian fairy tern. Although they are the same species they have brighter beaks and shorter eye patches so I modified the paint job a bit. The biggest difference between the sub-species seems to be that they flock together to nest. I imagine this will make the decoys more effective for this subspecies.

I lowered the design so it looks more like they are incubating, hopefully they will still turn into the wind ok. Photos below of the birds without spikes above and below.

PLA coated with two part epoxy resin then blasted with heat gun.

We’ve had some problems with these decoys, the black painted parts get so hot in Western Australia that the plastic melts leaving the decoys with flat hair cuts! The glass transition temperature for PLA is around 60° C. I tried covering some PLA with two part epoxy resin then warmed it up to try and simulate the issue. The epoxy worked well holding the form in shape even when I got it so hot the surface burned. However it did deform a little with bubbles and spilts, this might work as a patch up job but its not ideal, other ideas:

1. Changing the plumage to be less black (juvenile)
2. Printing with more infill (thicker heavier decoy)
3. Printing with another plastic
4. Creating moulds and using resins

I really like using PLA because it’s biodegradable and from a renewable resource but in this situation it just might not be up to the challenge. Common filament options are: ABS (won’t print with as good detail), PET (not glue-able) or Nylon (which has a lower glass temperature). I could print with plastic that has better thermal resistance like Polycarbonate, or print using dissolvable supports and no glue with something like PET but I would need a much more expensive printer. Unfortunately I think heat resistant decoys are going to be less environmentally friendly and either expensive or labour intensive 🙁

Update May 2019

Re-designed test decoys

I have made three new decoys to test, all are glued using two part epoxy.

  1. 40% infill and two coats of epoxy resin
  2. 20% infill and two coats of epoxy resin
  3. 40% infill

The numbers 1,2 & 3 are carved into the newly designed peg which is shorter but more heavy duty. The increased infill makes all of them heavier, this should help keep them down when the sand moves, if that does not work the painted legs should look more natural. The overall design of this decoy is a little more robust, it has it’s head ‘terned’ a little to help distinguish it from the other decoys I have made.

Update Dec 2019
These decoys were deployed from 3 Nov-20 December on Garden Island. They did not attract the target flock which nested elsewhere. With three of the days being in excess of 37 degrees the decoys got tested pretty well and show no signs of melting or splitting. They have been deployed in the researchers garden for further testing 😀

Photo by Claire Greenwell

Update April 2020

Decoy 2 developed a minor crack in the join, it was the weakest decoy with half as much infill for internal strength. No changes to the other two.