Fairy tern on the brink

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Neil Fitzgerald
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Re: Fairy tern on the brink

Postby Neil Fitzgerald » Fri Jan 18, 2019 8:08 pm

You should copy that to the Events board.
Ian Southey
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Re: Fairy tern on the brink

Postby Ian Southey » Sat Jan 19, 2019 9:12 am

I have been working on these birds for a few years now and I don't have the real depth of experience that some others do but I have a bit of time so here is my own 2c worth. People do work hard on this project, both DOC staff and volunteers and some serious thinking does go in to how to make things work better.

There was a major set back for Fairy Terns with 2 breeding seasons at Waipu from 2009 impacted by cat predation. Numbers of birds killed may not have been massive but they were mainly key breeding females and the population has been heavily male biased since this time. There was a loss of productivity in those two years and for another three breeding seasons after that until the number of females came back to it's previous level. Pairs moved from Waipu to Mangawhai during this predation event and the site has never recovered to the three breeding pairs it once supported. Now there is only one. In the meantime DOC has improved its trapping program considerably and there have been no major issues with terrestrial predators since that time. Gulls and Harriers are the main problems now. Temporary fencing might help but it might not produce enough added value and these birds are on and among active sand dunes so it might not work well any way.

There was a great breeding season in 2013-4 with 12 chicks fledging but all of the survivors were males. The following season started well and 11 chicks were banded but a severe late storm took five of them out and also a couple of breeding females. We were back to 10 pairs in 2017-8 and the population should be positioned to expand but it isn't happening.

The major problem at the moment is that that productivity of breeding birds has fallen of dramatically at Mangawhai and this is impacting the whole population. A major mangrove removal project in the mid reaches of the harbour there was immediately followed by a reduction in the numbers of eggs laid there, single eggs instead of two or one egg hatching and one egg not. In the past losses of nests often lead to birds nesting again but this has seldom happened since mangrove removal was completed and the impact is harbour wide. A recent DOC review pointed out that on average 6.4 Fairy Terns die each year and since mangrove removal at Mangawhai there have been no more than 6 chicks banded over the whole population in any year so the population has probably been in decline for about five years now but I don't have the actual numbers.

From what I have read about small tern species overseas it looks like mangrove removal has lead to a problem with the food supply and it is no longer sufficient when the birds are forming eggs. Sometimes chicks can be fed from the sea rather than the harbour but that is a less reliable food source. In my view it doesn't matter what the genetic quality of the birds is like if we can't recover their ability to lay eggs, hatch them and rear chicks. I think the existing birds show enough vigour to increase just fine but need a fair chance to show it.

These are what I think are the main things but they have a few more problems including having a habitat that people really like to play in and some congenital infertility. So far this season we have one chick banded and the possibility of one more. The problems seem to be too few eggs laid and avian predation, but in my experience it is a good idea to wait until the results of the breeding season have been collated and considered before jumping to conclusions.

People working with Fairy Terns have been focussed on small areas of interest, mainly based around breeding and protection of nests and a wider perspective is lacking. What has been missing in action is leadership and it is good to see DOC finally showing signs of stepping up to the mark (no pressure Troy!) but it's early days and it will take a while before there is any chance of meaningful results.

I am glad to see some thought going into this and maybe someone will have a good idea that could work. Probably the real challenge will be working around the people that live in these areas, at least until the population is able to expand again.

Ian

ps I really could use another person or two to help with the fish monitoring tomorrow. Please PM me if you are interested.
Jim_j
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Re: Fairy tern on the brink

Postby Jim_j » Sat Jan 19, 2019 10:32 am

Thanks very much Ian for taking the time to post this update.
All in all it seems there are multiple factors that sound very difficult to overcome.
Cheers Jim
Ian Southey
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Re: Fairy tern on the brink

Postby Ian Southey » Sun Jan 20, 2019 9:50 pm

I did hear today that the Waipu chick was banded late last week so it should be flying soon. Fingers crossed.

Ian
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Neil Fitzgerald
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Re: Fairy tern on the brink

Postby Neil Fitzgerald » Tue Feb 26, 2019 8:16 am

Ian and others discuss mangrove removal:

https://www.radionz.co.nz/news/national ... ve-removal
https://www.radionz.co.nz/national/prog ... rn-decline

The view of the "Restoration Society" secretary is.. umm.. disturbing.
Jim_j
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Re: Fairy tern on the brink

Postby Jim_j » Tue Feb 26, 2019 1:46 pm

Yes very disappointing.
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zarkov
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Re: Fairy tern on the brink

Postby zarkov » Tue Feb 26, 2019 5:24 pm

Mangawhai may be an exception, but large areas of mangroves growing in estuaries is a very recent phenomenon. Mangroves are indisputably a result of man made activity, silt and fertilizer runoff etc.

Fairy Terns were critically endangered everywhere long before any mangrove clearance, and if mangroves were beneficial you'd thing they'd be doing well in the Kaipara.

Probably historic pests, lack of dog control and more frequent NE gales has had more to do with their decline on the Mangawhai spit.
Jim_j
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Re: Fairy tern on the brink

Postby Jim_j » Tue Feb 26, 2019 5:47 pm

Yes a complicated situation
Possibly the increase in mangroves over recent years has provided a food source that compensated for our "General plundering of the ocean" , destruction of the marine environment. Etc etc

Cheers Jim
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Neil Fitzgerald
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Re: Fairy tern on the brink

Postby Neil Fitzgerald » Tue Feb 26, 2019 7:52 pm

They might have been endangered before mangrove removal, but that doesn't mean it won't break the camel's back.
Ian Southey
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Re: Fairy tern on the brink

Postby Ian Southey » Tue Feb 26, 2019 10:10 pm

I don't really understand the mangrove haters but perhaps it is worth pointing out that the importance of Mangawhai to Fairy Terns is a similarly recent phenomenon. It used to hold only one or two pairs.

Mangroves are the hallmark of northern estuaries with real benefits to wildlife, the fairy tern problems suggest their benefits also reach right out into the wider marine system and are not just confined to within their footprint. They don't mind the eutrophication as much as some species and causeways associated with roads make a nice sheltered habitat for them but fencing from stock has also helped them tremendously.

Ian

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