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Possible Salvin's Prion - South Atlantic - High Seas. (1 Viewer)
- Thread starter jmorlan
- Start date
This is going to be difficult. It has a ghost like quality to it and that highlights any light and dark areas on this bird.
Going with that, the highlighted tail surrounds could suggest Salvin's Prion. The head and in particular, the nape does not appear black, IMVHO you can rule out Blue Petrel. Also, the bill appears to be too thick for Slender-billed Prion.
The other possibility that I cannot rule out here is Antarctic Prion, as the face is very pale and the black band across the wings and rump appear to be fairly thin. I hope someone with more expierence than I will come along and confirm or refute your ID.
Going with that, the highlighted tail surrounds could suggest Salvin's Prion. The head and in particular, the nape does not appear black, IMVHO you can rule out Blue Petrel. Also, the bill appears to be too thick for Slender-billed Prion.
The other possibility that I cannot rule out here is Antarctic Prion, as the face is very pale and the black band across the wings and rump appear to be fairly thin. I hope someone with more expierence than I will come along and confirm or refute your ID.
Thanks for the reply. As far as I know, Antarctic Prion is not expected in this area. There are two (or three) likely candidates.
Broad-billed Prion
Broad-billed Prion (small-billed type recently described from Gough)
Salvin's Prion (race macgillivrayi) sometimes split as a separate species under the name MacGillivray's Prion or Saint Paul Prion.
My understanding is that Salvin's has a longer tail averaging more black at the tip and more white on the sides of the tail cf. Broad-billed. It also has a yellow slash on the side of the bill while Broad-billed has dark blue.
Broad-billed Prion
Broad-billed Prion (small-billed type recently described from Gough)
Salvin's Prion (race macgillivrayi) sometimes split as a separate species under the name MacGillivray's Prion or Saint Paul Prion.
My understanding is that Salvin's has a longer tail averaging more black at the tip and more white on the sides of the tail cf. Broad-billed. It also has a yellow slash on the side of the bill while Broad-billed has dark blue.
RafaelMatias
Unknown member
Prion ID and taxonomy is messy and still partial unfortunately.
The 3 options you point out are really the only ones to consider here imo. I'd say the bill is perhaps too deep at the base for "Saint Paul Prion", and that would place this (tentatively) within the Broad-billed Prion group (which indeed would be the expected "species" there). Photo quality doesn't make it easier also, in a group that is already difficult with perfectly crisp photos. Would there be any other photos?
The thing is that it's unknown whether those smaller billed Gough B-b Prions are even vittata (they breed 'together' with the large billed ones (morphs? genetically distinct?). They could eventually belong with "Saint Paul Prion", which in turn might not belong with Salvin's (could be a separate species, as you say). So, all very complicated at the moment, not helping to put a name in a single isolated bird at sea. On current knowledge, a large billed Prion in South Atlantic would be a Broad-billed (sensu lato), but who knows given the ID difficulties and sparse coverage by birders? Salvin's (Saint Paul's) would be out of range, but again who knows. And seabirds are prone to extreme vagrancy.
In favour of Broad-billed I'd include, besides the very deep base to the bill and range, the relatively weak dark carpal bar and the apparently extensive grey sides to the neck/upper chest, but these might be affected by photo artifacts in the present photo (even bill depth appearance perhaps). I can't make much of the tail (too affected by "ghosting").
The best field treatment of Prions is covered in "A complete guide to Antarctic Wildlife" (Shirihai), but even there it's not complete.
Here's a paper on the 2 "morphs" of Broad-billed from Gough (perhaps you already have it): http://sci-hub.hk/10.1007/s00300-014-1473-2
And some photos: http://chrisongough.blogspot.pt/2015/10/whalebird-of-south-atlantic-video-and.html
Photo 4 here (New Zealand) is not too different from your bird in bill depth and carpal bar intensity/darkness.
Very interesting nevertheless. Tubenoses are fascinating birds.
The 3 options you point out are really the only ones to consider here imo. I'd say the bill is perhaps too deep at the base for "Saint Paul Prion", and that would place this (tentatively) within the Broad-billed Prion group (which indeed would be the expected "species" there). Photo quality doesn't make it easier also, in a group that is already difficult with perfectly crisp photos. Would there be any other photos?
The thing is that it's unknown whether those smaller billed Gough B-b Prions are even vittata (they breed 'together' with the large billed ones (morphs? genetically distinct?). They could eventually belong with "Saint Paul Prion", which in turn might not belong with Salvin's (could be a separate species, as you say). So, all very complicated at the moment, not helping to put a name in a single isolated bird at sea. On current knowledge, a large billed Prion in South Atlantic would be a Broad-billed (sensu lato), but who knows given the ID difficulties and sparse coverage by birders? Salvin's (Saint Paul's) would be out of range, but again who knows. And seabirds are prone to extreme vagrancy.
In favour of Broad-billed I'd include, besides the very deep base to the bill and range, the relatively weak dark carpal bar and the apparently extensive grey sides to the neck/upper chest, but these might be affected by photo artifacts in the present photo (even bill depth appearance perhaps). I can't make much of the tail (too affected by "ghosting").
The best field treatment of Prions is covered in "A complete guide to Antarctic Wildlife" (Shirihai), but even there it's not complete.
Here's a paper on the 2 "morphs" of Broad-billed from Gough (perhaps you already have it): http://sci-hub.hk/10.1007/s00300-014-1473-2
And some photos: http://chrisongough.blogspot.pt/2015/10/whalebird-of-south-atlantic-video-and.html
Photo 4 here (New Zealand) is not too different from your bird in bill depth and carpal bar intensity/darkness.
Very interesting nevertheless. Tubenoses are fascinating birds.
Thanks for the helpful analysis. There are more photos. I don't think they are of much use, but here they are attached.
I agree completely that these are something of a taxonomic nightmare with the status of several populations uncertain.
I am confused by your assessment that Salvin's (MacGillivray's) would be out of range here. My understanding is that they breed commonly on Gough and (I think Tristan). Different experts on our ship seemed to have differing assessments of the prions we were seeing. Some thought they were mostly Broad-billed with maybe a few Salvin's. Others thought they were all or almost all Salvin's.
In looking at the photos of known Broad-billed from Gough (both bill types), I notice much less black on the tail tip and an apparently shorter tail than my bird.
I agree completely that these are something of a taxonomic nightmare with the status of several populations uncertain.
I am confused by your assessment that Salvin's (MacGillivray's) would be out of range here. My understanding is that they breed commonly on Gough and (I think Tristan). Different experts on our ship seemed to have differing assessments of the prions we were seeing. Some thought they were mostly Broad-billed with maybe a few Salvin's. Others thought they were all or almost all Salvin's.
In looking at the photos of known Broad-billed from Gough (both bill types), I notice much less black on the tail tip and an apparently shorter tail than my bird.
Attachments
RafaelMatias
Unknown member
I think the different nomenclature might be down to the taxonomic authority one's following. Some authors consider only 3 species of Prion to exist: vittata (including desolata and salvini, those becoming subspecies), belcheri, and turtur (including crassirostris); others consider 6 species to exist (e.g. see the treatment by IOC here, scroll down the page), each of them with several subspecies. Very complicated.
Note MacGillivray's (St. Paul Prion) is a very rare bird in global terms, with only 150-200 breeding pairs (plus an unknown numbers of nonbreeding immatures), and is an endemic breeder at Roche Quille, an offshore rock at St. Paul, central Southern Indian Ocean; Shirihai 2007). On the other hand, Salvin's (sensu stricto) have their westernmost breeding site at Prince Edward, SW Indian Ocean, reaching SE South Africa, but not going into the Atlantic (as far as it's known).
I'm guessing those people onboard were in fact referring to Broad-billed when they mentioned Salvin's. In the Atlantic, the only breeding large-billed prion is really Broad-billed (vittata), and that is the species (considering both morphs) to be expected, unless it's an odd vagrant.
I think going with Broad-billed for your bird would be a very safe bet.
Yes, there seems to be rampant confusion. When I suggest that the bird might be Salvin's, I am following Clements taxonomy which considers MacGillivray's to be a race. However, Clements and IOC have the ranges wrong. Macgillivray's Prion's only known breeding site is Gough where its population size is estimated at between 100,000 and 1 million mature individuals.
Some details at:
https://globally-threatened-bird-fo...st-concern-and-p-macgillivrayi-as-endangered/
See also: https://www.hbw.com/species/macgillivrays-prion-pachyptila-macgillivrayi
http://www.iucnredlist.org/details/104062579/0
The taxon in question here is MacGillivray's Prion as so defined and breeding on Gough.
Some details at:
https://globally-threatened-bird-fo...st-concern-and-p-macgillivrayi-as-endangered/
See also: https://www.hbw.com/species/macgillivrays-prion-pachyptila-macgillivrayi
http://www.iucnredlist.org/details/104062579/0
The taxon in question here is MacGillivray's Prion as so defined and breeding on Gough.
Last edited:
RafaelMatias
Unknown member
OK, so it seems that Prion taxonomy got even a bit more complicated during the last few years. I wasn't seeing this one coming.
This is what happened: Peter Ryan found that 2 morph of Broad-billed Prion were breeding alongside on Gough in 2014 (paper above). On that paper he points out that the smaller billed form is morphologically similar to the birds breeding in St Paul (MacGillivray's Prion, Southern Indian Ocean, 200 breeding pairs, as above). From his own (P. Ryan) unpublished data he assumes on the year after (Dilley et al. 2015, see below) that they are so close morphologically that they must be indeed be MacGillivray's Prions; however that is a paper on breeding ecology with no data presented (molecular, biometrics, etc) to sustain the assumption.
Dilley et al. 2015. Effects of mouse predation on burrowing petrel chicks at Gough Island. PDF
and
I'm not aware of any molecular data comparing both forms on Gough (and MacGillivray's compared to Salvin's), but BirdLife/IUCN proceeded not only with the split based on the above paper (and personal info from Peter Ryan) as also with lumping the smaller billed morph of Gough with MacGillivray's Prion sensu stricto (those on St. Paul).
In the Birdlife forum news you posted above they (Rocio Moreno) say:
This doesn't make complete sense to me.
And they add:
This is basically wrong or misleading in my opinion. The type specimen of MacGillivray's Prion comes from St. Paul, an thus it is not the small population breeding on St. Paul that needs to have its taxonomic status resolved (which is MacGillivray's Prion sensu stricto), but clearly those on Gough. Those on Gough are the ones that may be MacGillivray's or not, the ones at St. Paul are of course certain MacGillivray's. What a mess!
HBW has a bit more cautious approach:
Note the distribution map shows it as breeding on Gough as well, contradicting the text.
I wonder if there's even enough info to consider it monotypic, given we just don't know.
In the end they may all be MacGillivray's Prions (those on Gough), but this is not the way to solve the issue properly, imo. A bit of a mess, but I trust they know what they're doing. This obviously has serious conservation implications, as MacGillivray's Prion would have it's known world population increased by a mere 1 million pairs (potentially causing the St. Paul population to be neglected).
I hope I didn't contribute to confuse you with this lengthy reply. I'll be waiting for molecular data to put a name on those Gough birds though.
Thanks for the helpful clarifications. I think you have analyzed the situation correctly, and I have some of the same doubts as those you expressed. Personally I like the way eBird/Clements have handled the situation. They leave MacGillivray's as a subspecies of Salvin's confined to the Indian Ocean. The Gough birds are listed as:
Gough Prion (undescribed form)
They are correct that this form has never been formally described and further research is needed to clarify its taxonomic position.
In the meantime, I have changed the ID of the prion I photographed to "Gough Prion (undescribed form)". So to rephrase my original question. Do I have that right? Is this bird a reasonable match for Gough Prion? The alternative is the original Broad-billed Prion with the huge all-black bill.
Thanks for all your help. Much appreciated.
Gough Prion (undescribed form)
They are correct that this form has never been formally described and further research is needed to clarify its taxonomic position.
In the meantime, I have changed the ID of the prion I photographed to "Gough Prion (undescribed form)". So to rephrase my original question. Do I have that right? Is this bird a reasonable match for Gough Prion? The alternative is the original Broad-billed Prion with the huge all-black bill.
Thanks for all your help. Much appreciated.
