North/South Island endemics and the Cook Straight

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North/South Island endemics and the Cook Straight

Postby fras444 » Sat May 05, 2018 8:56 pm

Coming up with a headline for this topic was the hardest part...
Topic I would love to create and that is...

The history of Endemic North/South Island birds, How and why some Endemic birds... well the only I can think off.. Blackbilled gulls... decided to breed on the north Island and what's stopping the SIPO/wrybill etc from doing the same, what Island endemics have crossed the devide to loose the status of being endemic to the North/South and what birds could become the next to make home in the North/South.... Have there ever been vagrants of the brown creeper/Whitehead etc... What's stopping a certain species (a wind could blow a small flock Whithead astray or a pair of Creasted greabs....) Could the king Shag make the Wellington heads home...

With 1900kms of ocean between Austrailia and NZ how Significant is the Cook Straight and endemic bird species of North and South Island
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Re: North/South Island endemics and the Cook Straight

Postby RussCannings » Sun May 06, 2018 10:10 am

Hi Fras,

Many of these questions are answerable through research. NZ for example is just one of multi-island countries that has island-specific endemics. Sometime these birds spread their range elsewhere, sometimes they dont. Black-billed Gulls and SIPO (the latter has attempted breeding in various North Island east coast locations sporadically since the 80s as stated on nzbirdsonline) and this is not surprising as strong fliers that like coastal locations. Whitehead and Brown Creeper on the other hand are not known for their strong flight and they would much rather be in dense native bush then flitting over beaches, cliffs, and ocean. (A similar example from my home province of British Columbia: Black-capped Chickadee is possibly the most common bird in Vancouver yet there are ZERO records for Vancouver Island--an hours ferry away). So things like rock wren, creeper, or Hawaiian honeycreepers on the islands they are because that's where they evolved. Maybe one day they will pop over but until they do they'll be right where they are ;) I'm not trying to be cheeky, just stating the simple fact that small non-migratory forest passerines are not the greatest bets for vagrancy let alone establishing new breeding colonies. That's why no one is holding their breath for the first aussie scrub wren to touch down on our shores. Crazier things have happened though! I suspect wrybill probably did breed occasionally on the manawatu and hawkes bay rivers way back in the day when their numbers nationally were higher. That's just a hunch but anyhow. They seem to like those south island rivers so good on em.

FYI Crested grebes are not South Island endemics as they not only historically bred on the North Island (and still occur as vagrants) but they're widespread in Aussie. As for King Shag, I believe the conventional wisdom is that this is a tiny remnant population of a much more significant range that would have originally connected them with Stewart Island Shags (Now being split further between Otago and Stewie populations). So they probably did best in Wellington 2000+ years ago maybe but there's so few of them now they're not a great candidate for territorial expansion.

Just a few Sunday thoughts from me anyway. Interesting topic.

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Re: North/South Island endemics and the Cook Straight

Postby Jim_j » Sun May 06, 2018 10:44 am

Yes you do need to be a bit careful - the current distribution may not reflect the historic one.

I'm sure it's possible that over the millennia a few W/Head ended up in the SI and a few Y/Head and Brown Creeper went the other way - but with their ecological niche already taken they would have just died out.

I hate to say this not being the best speller meself but - Cook Strait..

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Re: North/South Island endemics and the Cook Straight

Postby Davidthomas » Sun May 06, 2018 11:52 am

I know that there are historical records of Wrybill breeding in the north island from the late 1800s, and blackfronted terns used to breed in the Hawkes Bay until the mid 1900s I think.
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Re: North/South Island endemics and the Cook Straight

Postby Michael Szabo » Sun May 06, 2018 3:21 pm

Fairy Tern and Shore Plover were also recorded breeding in the North Is and South Is in the 1800s.
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Re: North/South Island endemics and the Cook Straight

Postby simon.fordham » Sun May 06, 2018 4:51 pm

RussCannings wrote: As for King Shag, I believe the conventional wisdom is that this is a tiny remnant population of a much more significant range .....

King shag bones were identified, some 20 years ago, in middens on Tiritiri Matangi Island.

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Re: North/South Island endemics and the Cook Straight

Postby andrewcrossland » Sun May 06, 2018 8:53 pm

"Historical records of wrybill nesting in the North Island"??? Is that record taken from a Tui's billboard? Back in the 1930s (before the rediscovery of the major wintering flocks in the Auckland region by Sibson etc) a lot of mystery surrounded wrybill and many writers of the day had to refer back to Potts etc , to regurgitate all that was known of them. In the late 1800s and early 1900s they were occasionally recorded on both east and west coasts of the lower north island (we know now ofcourse that these were birds I'm transit and sites like manawatu estuary and porangahau still annually host wrybill). But there are no bonefide north island breeding records - unless that's a secret that's been held on to tightly for 140 years?

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