A Most Unusual Diving Petrel

General birdwatching discussion, help with bird identification, and all other things relating to wild birds and birding in NZ that don't fit in one of the other forums.
Ian McLean
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Joined: Sat May 11, 2013 2:29 pm

A Most Unusual Diving Petrel

Postby Ian McLean » Sun Aug 18, 2019 10:24 pm

Hi there
The Auckland branch of Birds New Zealand conducted one of our regular patrols of Muriwai Beach on Saturday the 10 of August. Our tally of birds included: 1 Buller’s Albatross, 2 Fluttering Shearwater, 24 Fairy Prion, 6 Slender Billed Prion, 1 Prion sp & 5 Common Diving Petrel.

I took three of the Diving Petrels home to take to the Auckland Museum & whilst checking them I noticed that one was very different to the other two Common Diving Petrels.

Please note the three photos for your reference. The unusual bird is the top bird in the photo of three.

The differences between this bird & the other two Common Diving Petrels are as follows:-

-It had a larger head & different profile.
-It had more white feathers on its underwings (like a South Georgian Diving Petrel)
-It had shorter wings of only 122mm, compared to the other birds which had wing measurements of 130mm & 135mm.
-The bill profile was different, although I have no bill profile cards of either Common Diving Petrel or the South Georgian Diving Petrel.
-The bill of the Common Diving Petrel had light blue on the lower mandible, whilst the odd bird had much less.
-The legs of both of the Common Diving Petrels were light blue, whilst those of the odd bird were darker & especially so on the webbing. (Note that this may be due to a different level of decomposition, although the odd bird appeared the freshest specimen).
-It had more white feathers around its face compared to the others.

These differences may indicate that the odd bird is a South Georgian Diving Petrel, but I am not sure ? Another possibility is that it could be one of the critically endangered & endemic Whenua Hou Diving Petrels ? I have no details on many of the distinguishing features of the Whenua Hou birds & wondered if there was a small possibility that this odd bird could be one ?

I would very much appreciate any comments & thoughts about this bird.

The good news is that all three birds will be taken to the Auckland Museum & they can hopefully solve the mystery of this bird !

Cheers
Ian McLean
Diving Petrel head (Common Diving Petrel).jpg
The head of one of the Common Diving Petrels.
Diving Petrel head (Common Diving Petrel).jpg (350.42 KiB) Viewed 539 times
Diving Petrel head (odd one).jpg
The head of the odd bird.
Diving Petrel head (odd one).jpg (460.31 KiB) Viewed 539 times
Diving Petrels x 3.jpg
Two Common Diving Petrels at the bottom with the odd bird at the top.
Diving Petrels x 3.jpg (490.06 KiB) Viewed 539 times
Steve Wood
Posts: 172
Joined: Sat Dec 05, 2009 6:57 pm

Re: A Most Unusual Diving Petrel

Postby Steve Wood » Mon Aug 19, 2019 9:15 pm

Hi Johannes, thanks for your comments.

Is it possible to provide any pics that would illustrate the differences you described of the bills from above of CDP and WHDP please ?

Also could you clarify please. After all the great work that you guys have done regarding the D Pets on codfish - I see you still referenced SGDP, are you suggesting they are still a realistic possibility in NZ?... and if so are there any excepted records of SGDP in NZ ?... or were the historical records that were thought to be SGDP a miss id and are in fact now confirmed to be all WHDPs.

Thanks for clearing this up.
Colin Miskelly
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Joined: Sat Jul 11, 2009 6:31 pm

Re: A Most Unusual Diving Petrel

Postby Colin Miskelly » Mon Aug 19, 2019 9:20 pm

Hi all
The only form of 'South Georgian diving petrel' recorded from New Zealand is the bird now known as Whenua Hou diving petrel.
Cheers
Colin
Steve Wood
Posts: 172
Joined: Sat Dec 05, 2009 6:57 pm

Re: A Most Unusual Diving Petrel

Postby Steve Wood » Mon Aug 19, 2019 9:22 pm

Thanks for clearing that up Colin.
Ian McLean
Posts: 51
Joined: Sat May 11, 2013 2:29 pm

Re: A Most Unusual Diving Petrel

Postby Ian McLean » Mon Aug 19, 2019 10:11 pm

Kia ora Johannes

Thanks very much for your comments & the great information, it's most appreciated !

This evening I had a dig thru my beer fridge freezer & had another look at the Diving Petrels. They were bagged up underneath a Black Browed Albatross & are now rather frozen solid. So not the best to photograph, but I have attached a photo of the exsul or chathamensis bird. The photo is a poor one, but as you describe the bird has the same nostrils as a Common Diving Petrel urinatrix.

I also found an excellent guide to the bill shapes of Diving-petrels in a fabulous book by Peter Harrison called "Seabirds an identification guide" which was first published in 1983 & I recently bought second hand

Thanks for all your help, I can know confirm that the bird is a Common Diving Petrel exsul or chathamensis & not the urinatrix subspecies that we normally find around Auckland. The shape of the head, shorter wings & whiter underwings had me thinking I may have had something very different, but its been a great learning experience & I will be paying close attention to others I find.

Cheers
Ian McLean
Diving Petrel bill (odd one).jpg
Common Diving Petrel exsul or chathamensis bill
Diving Petrel bill (odd one).jpg (326.13 KiB) Viewed 380 times
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Neil Fitzgerald
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Re: A Most Unusual Diving Petrel

Postby Neil Fitzgerald » Wed Aug 21, 2019 8:14 am

Colin, SGDP page on NZBO needs updating?
Colin Miskelly
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Re: A Most Unusual Diving Petrel

Postby Colin Miskelly » Wed Aug 21, 2019 11:48 am

Hi Neil

Yes, it does.

I occasionally agitate for contributing authors to update their texts for NZ Birds Online. While (as editor) I could update texts and then advise the relevant authors that I have been tinkering with their pages, this is very time consuming to do in a systematic way, and it is the species experts who are best placed to recommend changes. I am happy to fix errors (e.g. typos) when they are brought to my attention, but if you seek updates (e.g. new published information that should be included), please contact the relevant author with your suggestions.

I have been reluctant to change nomenclature on the website ahead of the Checklist Committee recommending changes in a publication. The Birds New Zealand (OSNZ) Checklist/Checklist Committee should be the authoritative source for New Zealand bird names, not a website like NZ Birds Online or Wikipedia. The Checklist Committee have had a draft update in production for years. Further delays in this being finalised may force my hand with widely accepted nomenclatural changes, but again I am wary of cherry-picking changes where it could be perceived that I am individually supporting or agreeing with the change (and by implication, disagreeing with others). The preferred solution is a simultaneous update of names across the website based on an a single authoritative source.

Cheers
Colin
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Neil Fitzgerald
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Re: A Most Unusual Diving Petrel

Postby Neil Fitzgerald » Wed Aug 21, 2019 12:34 pm

I'm probably as guilty as anyone. A new checklist would be good.

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