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Thread: Pterodroma

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    Senior Member Alex Lees's Avatar
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    Default Pterodroma

    Of interest to North Atlantic Pterodromaphiles is this paper: Zino et al. (2008) attached. They have this to say on the field identification of this pair:

    "The separation of Zino's and Fea's Petrels in flight has been much debated amongst experienced ornithologists and birdwatchers (Fisher 1989, Gantlett 1995, Tove 1997, 2001, Steele 2006). From the biometrics analysed, the bill is by far the easiest form of differentiating the two species, but for an observer in the field this is difficult. Using digital photography and image analysis, Tove (2001) demonstrated that there are differences in the shape of the wings of these species. The relative primary lengths measured (Appendix 1) confirm this, the tip of the wing of P. madeira being rounder, but such technology is available to few people. Wing feather pattern in the sample studied showed a large individual variation with very similar patterns in both species (Fig. 6). Steele (2006) discusses the problem at length and is in agreement that it is still nearly impossible to differentiate between P. madeira and P. feae in flight."

    Alex
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    Last edited by Alex Lees; March 28th, 2008 at 11:41 AM.
    Dept. of Zoology, University of Cambridge, UK

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    In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

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    Moderator Brian S's Avatar
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    Alex

    Though I have read this and all of the references before, my field experience of Zino's and Fea's is restricted - and judging by these comments on field identification, I should not have been able to be certain of those I have seen.

    However, my eyes were opened in 2005, when leading a group on Madeira in late May. One evening, having seen many Cory's, Manx and a few 'Little' Shearwaters, plus Bulwer's Petrels, we saw two Pterodroma south of Funchal. The most remarkable thing about them were their apparent size: not wing-span, but the bulk of their bodies. We felt that in body size they were substantially smaller than Manx and actually almost as slight as the 'Little'; there was no heavy, barrel chest at all and it was a really distinct feature of the two birds.

    On our return, I checked the weights of Fea's and Zino's against Manx and Little (so much of the literature concentrates on the biometry of wing length, but as an artist I know that weight is actually a very significant consideration). The means below of various published weights give some idea of the comparative body size.

    Manx Shearwater - c.410 g
    Fea’s Petrel - c.310 g
    Zino’s Petrel - c.203 g
    'Little' Shearwater - ? (but HBW gives '170-205g', let's say a mean of c.188g).
    [I hope that someone might be able to post some better weight figures than I have access to here].

    From these I feel that Zino's is substantially smaller than Manx Shearwater, significantly smaller than Fea's, but only slightly heavier than 'Little'. Many published descriptions of Fea's (cf. Steele 2006) in Britain give a body size and bulk similar to Manx (averaging slightly smaller), but the birds I saw off Madeira were distinctly slimmer than Manx, and I would probably identify them as Zino's on this feature - albeit a little tentatively.

    Brian S

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    Senior Member Alex Lees's Avatar
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    Hi Brian

    Some interesting observations that parallel Ned Brinkley's notes on a presumed Zino's at sea in late April. I believe one of the Strumble Head stalwarts once saw a Pterodroma that he felt was more Zino's than Fea's. They ought to sat-tag a few Zino's to see what they get up to....

    cheers

    Alex
    Dept. of Zoology, University of Cambridge, UK

    My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

    In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

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    Moderator Brian S's Avatar
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    Alex

    I have a confidential photo of one in the Atlantic at 49 degrees north (level with Scilly?)! Definitely worth keeping an eye out for them.

    Brian S

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    Senior Member Alex Lees's Avatar
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    Quote Originally Posted by Brian S View Post
    Alex

    I have a confidential photo of one in the Atlantic at 49 degrees north (level with Scilly?)! Definitely worth keeping an eye out for them.

    Brian S

    Hi Brian

    If you are referring to Mick Mackey's image of the bird photographed (crisp flight shot under a Great Shear) from aboard the RRS James over the Mid Atlantic Ridge (approx 49N, 29W) last summer then I've got a copy too..... the bill is certainly mega small...

    Alex
    Dept. of Zoology, University of Cambridge, UK

    My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

    In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

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    Senior Member Martin Scott's Avatar
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    I always found it odd that it took a photo of one in the UK before the committee accepted a Fea's, based primarily on bill size.

    However in Jimmy Steele's paper it lists lots of records that clearly stated heavy bill, structure etc, but clearly it was felt prudent to wait till a photo appearred.

    Firstly rather biased against those who dont take photos, and secondly from that are commitees saying you must have a pic of the bill to show its structure rather than notes? Or is this just part of the 'must have a photo' culture now swamping birding?

    Brian - is there any likliehood of going back over all the 90's records etc that don't have photo's and accepting them to species level?

    By the way is this other 'confidential' photo ever going to appear in the public domain?

    MSS

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    Senior Member Alex Lees's Avatar
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    Quote Originally Posted by Martin Scott View Post
    I always found it odd that it took a photo of one in the UK before the committee accepted a Fea's, based primarily on bill size.

    However in Jimmy Steele's paper it lists lots of records that clearly stated heavy bill, structure etc, but clearly it was felt prudent to wait till a photo appearred.

    Firstly rather biased against those who dont take photos, and secondly from that are commitees saying you must have a pic of the bill to show its structure rather than notes? Or is this just part of the 'must have a photo' culture now swamping birding?

    Brian - is there any likliehood of going back over all the 90's records etc that don't have photo's and accepting them to species level?

    By the way is this other 'confidential' photo ever going to appear in the public domain?

    MSS
    Hi Martin

    I guess that the August record will be published in due course, so I'm sure you won't have long to wait. Correct me if I'm wrong, but weren't the accepted records the first to be seen well, ie at sea, at close range and for a protracted period (as well as photographed). Zino has already outlined how difficult their field separation is, so I would be certainly side with the committee on this one.

    cheers

    Alex
    Dept. of Zoology, University of Cambridge, UK

    My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

    In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

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    Moderator Brian S's Avatar
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    Alex, you say, 'If you are referring to Mick Mackey's image of the bird photographed (crisp flight shot under a Great Shear) from aboard the RRS James over the Mid Atlantic Ridge (approx 49N, 29W) last summer then I've got a copy too..... the bill is certainly mega small...'

    So much for my 'confidential image' It is not just the bill, the whole body of this bird looks very slim - sorry to those that haven't seen it!

    To reply to Martin's comments about descriptions of heavy bill, it should be realised that the first record, the Scilly bird, was not photographed/filmed well enough to exactly establish the bill shape and this was on a bird very much closer than those passing headlands. The drawings of the bill got the Scilly record accepted as Fea's, but surely it is to some extent wishful thinking to describe exactly the bill of a bird passing 600m+ at sea - certainly not well enough to rule out Zino's. I do however, personally believe that as the all descriptions suggest that the size was that of a Manx, they may well have been Fea's, but no more than that....I'm also with the BBRC on this one

    Brian S

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    Senior Member Martin Scott's Avatar
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    Quote Originally Posted by Alex Lees View Post
    Hi Martin

    I guess that the August record will be published in due course, so I'm sure you won't have long to wait. Correct me if I'm wrong, but weren't the accepted records the first to be seen well, ie at sea, at close range and for a protracted period (as well as photographed). Zino has already outlined how difficult their field separation is, so I would be certainly side with the committee on this one.

    cheers

    Alex
    Depends on your definition of "well". Does 30 foot off the back of a boat on Aug 31st 1999 constitute well?!

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    Senior Member Alex Lees's Avatar
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    Quote Originally Posted by Martin Scott View Post
    Depends on your definition of "well". Does 30 foot off the back of a boat on Aug 31st 1999 constitute well?!
    Hi Martin

    That was a disclaimer! Checking the records then, there are four boat-based observations of Fea's/Zinos that predate the accepted records:

    2000 At sea Sea area Malin, 56 km SW of Aranmore Island, Donegal, 18th August. P. Milne, Irish Birds 7: 220

    1999 Scilly About 5 km S of St Agnes, 31st August. M. J. Rogers and the Rarities Committee, British Birds 94: 455

    1999 Scilly About 1.5 km S of Bishop Rock, 24th August. M. J. Rogers and the Rarities Committee, British Birds 95: 479

    1996 At sea Sea area Fair Isle, 130 km WNW of Unst, Shetland, 60°57'N 3°05'W, 25th June. M. J. Rogers and the Rarities Committee, British Birds 90: 457

    So, none of these were photographed, although several may have been seen well, I guess its up to the committee whether any review is in order, only one of which (your one) was apparently multi-observed (from what I can discern).

    cheers

    Alex
    Dept. of Zoology, University of Cambridge, UK

    My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

    In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

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