Endemic NZ Swan

Discussion about the evolution, relationships, and naming of New Zealand birds
Alan Tennyson
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Joined: Mon Sep 20, 2010 1:54 pm

Re: Endemic NZ Swan

Postby Alan Tennyson » Mon Aug 07, 2017 3:21 pm

Jim - I would presume that the extinct swan filled a fairly similar niche to the black swan and so, although the black swan occasionally arrived from across the Tasman, there was no room for it to muscle in until the NZ endemic became extinct. So, yes, the habitat may not have changed much for swans but the back swan would not have established here without human modification.

Ian - I'm basing my conclusion that the black swan is 'native' on what's published by others. I haven't examined the original records in detail myself. It may be true that the black swan established solely from introductions but it sounds as though we might never know.
Byrd
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Location: Christchurch

Re: Endemic NZ Swan

Postby Byrd » Tue Aug 08, 2017 10:09 am

regarding introduced numbers, Christopher Lever's "Naturalised Birds of the World" - which is generally accurate and well-researched - says (in part) "the earliest documented importation took place shortly before 1864 when seven birds were acquired by the Nelson Acclimatisation Society ... In that year the governor of New Zealand, Sir George Grey, presented four birds to the Canterbury Acclimatisation Society, and in 1865 13 pairs were obtained by the Christchurch City Council, which released them in the Avon River ... The numbers of Black Swans increased dramatically, and in 1867 many birds dispersed to Lake Ellesmere, Marlborough, Otago and the west coast ... By 1880, up to 500 individuals were established on the Rivers Avon, Halswell and Heathcote, and within 15 years several thousand had colonised the estuary of the Opawa River in Marlborough ... Between 1866 and 1870 the Otago Acclimatisation Society released a total of 61 and in 1869 half-a-dozen were released by the Southland Society ... Black Swans were first introduced to North Island in 1864 (Buller 1872) or 1867 (Thomson 1922) when the Auckland Society released four ... "
through the course of evolution lemurs became monkeys, monkeys became apes, apes became man, and man became a jerk.
andrewcrossland
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Location: Christchurch

Re: Endemic NZ Swan

Postby andrewcrossland » Sat Aug 12, 2017 7:08 pm

Even assuming every released black swan survived, found a mate and bred prolifically, the sheer increase in numbers in such a short space of time simply can't be credited to the introduced birds. The Avon river ones (whether it be 13 or 14 birds or 14 pairs) all flew to various points of the compass within a short space of time so it's hard to believe survival was high and they formed a prodigious breeding nucleas.
I wonder if there was a series of good breeding years followed by drought in Australia during the period black Swan appeared in nz? Note that white-eyed duck and red-necked avocet were trying to establish in nz at that time and I wonder how this period synchronizes with influxes of royal spoonbill, grey teal, pukeko, little black cormorant,
and white-faced heron (there are many records pre 1940s which seem to be ignored ) etc?
Ian Southey
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Re: Endemic NZ Swan

Postby Ian Southey » Sun Aug 13, 2017 8:23 am

Andrew

Anything is possible and your scenario is indeed reasonable, but I think, not necessary. Starting with what we know is true - that a lot of birds were released and that they have the potential to breed prolifically (I don't think spreading "to various points of the compass" precludes that) I think that there is no need to make stuff up. Exponential population only looks slow for a few years and then numbers go through the roof quite quickly. Look at the spoonbill population now for an example but note that the capacity of swans to increase is much greater.

As far as I know all of sightings follow the liberations.

Ian
Jim_j
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Re: Endemic NZ Swan

Postby Jim_j » Sun Aug 13, 2017 12:20 pm

While I tend to agree with you Ian - choosing Spoonbill as an example of rapid growth is probably not the best example.
If anything this supports Andrew's theory - likely on-going influx from Australia.
Part of the issue could also be the reliability of early counts - swans are mobile birds and may have appeared more numerous than they were?

However I still believe that the introduction of this species (natural or not) is a good early example of ecological "repair" - it filled the vacant niche of the NZ endemic swan (if indeed that is what it was - given the rate at which theories change in the scientific world!!), apparently exterminated by human hunting pressure - it was not an introduced species that relied on a natural environment changed by humans.

cheers
jim
Ian Southey
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Joined: Tue Sep 08, 2009 5:45 pm

Re: Endemic NZ Swan

Postby Ian Southey » Sun Jul 15, 2018 5:25 pm

Seems like there has been a little more controversy about the genetic makeup and history of the New Zealand Black Swan

https://onlinelibrary.wiley.com/doi/epd ... /eva.12535

https://www.researchgate.net/publicatio ... tano_et_al

https://www.researchgate.net/publicatio ... lack_swans

Ian
Jim_j
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Re: Endemic NZ Swan

Postby Jim_j » Mon Jul 16, 2018 2:26 pm

Thanks Ian.
I must admit I find the hypothesis a little beyond belief!
Black swans are fairly large obvious birds - surely there would have been some sightings if a population had persisted in NZ prir to the re-introductions.

cheers
Jim

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