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.

A decoy dotterel

I have been working with Northern New Zealand dotterel (NNZD) for nearly five years now. I know this bird really well but I had to look a lot closer when I decided to try and make a decoy. Southern New Zealand dotterel (SNZD) are in big trouble with a small and declining population. I decided to see if a decoy would work to help capture SNZD which have been difficult to catch outside of breeding season. A well placed decoy could help position one or more birds near a leg-hold noose-mat trap or in position for a canon net.

I put the decoy about 20m away from some NNZD at Point England and on both occasions each NNZD walked over to the decoy (with head bobs) in less than two minutes. They stayed just less than 1M away for two minutes before I removed the decoy.

I need to fix the beak, refine the plumage and add spikes to the removable legs but so far it looks promising.

UPDATE: I have made a small flock of them. They are not quite right but should do the job.

Resilience

The population of any given species needs to be strong enough to handle destructive natural and made made events. Without this resilience one event can wipe a species of the face of the planet forever. In New Zealand our rarest endemic breeding bird is the New Zealand fairy tern. With a population of only 40 birds this is the breakdown for the 2017-18 season.

  • 3-4 of last seasons surviving chicks which are too young to breed
  • 1 menopausal female
  • 1-2 ‘engaged’ couples who behave like they are breeding but do not lay eggs
  • 11-14 unpartnered males (the population is short on females)
  • 20 breeding birds (10 pairs)
  • It’s a fragile population with too many males (1:2 ratio). The other major concern is that during breeding season 80% of the population is on the same 40km stretch of coast. Here is where the breeding happened in 2017-18:

    East coast:
    Waipu 2
    Mangawhai 5
    Pakiri 1

    West coast:
    Papakanui 2

    The fragility is particularly exposed when we think about the threat of an oil spill from the RMS Niagara. This wreck is a time bomb just off the coast from this critical breeding habitat. Even a small amount of the submerged oil could easily cover the fairy terns breeding grounds for weeks, starving the birds to death in a matter of days.

    An explorer in a land of herps: discovering lizards in Aotearoa/New Zealand

    Book recommendation: This book by a NZ adventurer and herpetologist is awesome. It’s a refreshingly honest collection of great adventures and scientific discoveries. I throughly enjoyed Tony’s detailed descriptions of New Zealand’s treasures, his passion is inspirational. I really appreciated him sharing the highs & lows of what has been an outstanding career… so far. Get it here.