Prion ID (1 Viewer)

[Jon.Bryant]

In December I was on the Heritage Expedition trip to the Subantarctic Islands. We saw Broad-billed, Antarctic, Fulmar and Fairy Prions, but when searching though my wife's photos, I have found a few birds that really puzzle me.

Firstly there are at least three birds that do not look that broad-billed (perhaps more like Antarctic in bill size), but have strong moustacial lines and very steep 'bulbous' foreheads. Could these birds be Salvin's Prion's - this species visits NZ waters, but should be absent in December. See pictures below - of these, the last bird at Enderby seems to be the most hopeful for the species - very white lores, strong super and small dusky nail compared to bulbous pale nail of Antarctic. The others have smudgier faces and I suppose could be Broad-billed at an angle where the bill is not that distinct (but they just don't look right to me).

Bird near to Macquarie Island


Bird near to Campbell Island




Bird near to Enderby Island




Secondly we have this bird, which looks to me like Slender-billed (which I have seen before in the South Atlantic). Again Slender-billed should not be present in December, but are present in New Zealand waters at other times of year. This seems more of an obvious one to me, but any comments would be welcome.

Bird on right with Antarctic on left





Bird on left with Antarctic on right

 

[Paul Chapman]

Jon

Not sure if you have seen the attached paper. Otherwise, I have been using The Australian Bird Guide.

I would say your first bird near Macquarie is the one most interesting as a potential Salvin's Prion on bill shape and undertail and only some of the latter pics look interesting as a potential Slender-billed Prion. Otherwise, I struggle to see much difference in bill shape with the accompanying bird. I also wonder if Slender-billed should appear smaller in most circumstances in comparison to Antarctic.

Out of interest, where was the potential Slender-billed Prion photographed and are you sure all pics (both sides of the Antarctic Prion) relate to the same bird?

The potential Slender-billed Prion photographed by my travelling companion was early on 9th December so again around Macquarie.

What I consider to be Fairy, Fulmar, Antarctic & Broad-billed Prions in that order are attached from my pics. If your birds are not more interesting, they would be Antarctic Prions in my view. Most of my pics were of Antarctic Prions & appear very variable.

All the best

Paul

 

[Jon.Bryant]

Out of interest, where was the potential Slender-billed Prion photographed and are you sure all pics (both sides of the Antarctic Prion) relate to the same bird?

Hi Paul,

I think they do. I wasn't taking the photographs, but the timing on the full sequence of shots and the position between frames suggest it is the same bird.

Not sure if you have seen the attached paper. Otherwise, I have been using The Australian Bird Guide.

The main reference I have used is 'Oceanic Birds of the World' (Steve N.G.Howell & Kirk Zufelt) [OBotW]. I have also referenced 'Seabirds - The New Identification Guide' (Harrison, Perrow and Larsson) [SNIG]. Unfortunately, I cannot easily read the photo you attached, but I think that the OBotW and your paper basically align in that;

Salvin's verses Antarctic

• Antarctic normally shows a bulbous pale nail to the bill, whereas Salvin's shows a darker grey less bulbous nail.
• Salvin's can show a quite pronounced smile line, which seems to be at best is slight and short in Antarctic.
• The bill of Salvin's 'averages' wider and stouter.
• SNIG also suggested Salvin's is 'larger headed with steeper, swollen forehead, larger blue bill and whiter, white cleaner face....'.

In OBotW all of the Salvin's photos show some form of smile line (but this is less distinct in some birds), whereas the Antarctic photos show at best a faint short line (1 in 11 photos). So a big question for me is whether a distinct smile line (and lack of pale bulbous nail), are diagnostic of Salvin's (or Broad-billed).

To eliminate Broad-billed, I think that the bills appear not grotesque enough, and also Broad-billed reportedly has a duskier face with darker lores - Salvin's is stated to have whiter lores - these descriptions are in both OBotW and SNIG.

In my opinion the bird near Macquarie and Enderby seem to be the most interesting - the other bird does seem to show a rather pale nail (but perhaps this is just the light).

Slender-billed verse Antarctic - I don't think this is covered in your paper extract. But my references state

• Slender-billed has a broad-white eyebrow, white lores and narrow dark eyestripe (typically narrower than the supercillum).
• Slender-billed has a narrower and rather slender (but dimensions overlap with some Antarctic Prions).
• Antarctic is also slightly stockier and bigger headed than Slender-billed.
• OBotW states that the forehead is often rather steep and squared in Slender-billed, and that the dark eyestripe is typically narrower than the white brow.

To me the bill is quite odd in Slender-billed - It shouldn't really be called Slender-billed but instead Narrow-billed! In side on photos that I have studied, the bill is not always distinctly shallower that Antarctic - perhaps marginally shallower at the base, and a bit more shapely (less triangular in shape), with more of a step in depth past the nostril and with more of a hook tip. In some photos the bills of Slender-billed look truly 'slender', but I think this depends on the tilt of the head, and whether the 'narrowness' of the bill influences the view. I therefore suspect the impression of the bill can vary when viewing the same bird.

OBtoW warns that Indian Ocean Antarctic can approach the head pattern of Slender-billed, but the only photo they provide is not as clean as the bird my wife photographed.

To me the bird does seem to show the correct head pattern, and does appear slightly smaller headed and less stocky that the accompanying Antarctic - the accompanying Antarctic seems to me to be more bull necked, slightly wider on the hips and perhaps a touch wider winged. The head also seem rather square as suggested by SNIG. This combined with the occasional 'slender-billed impression', still makes me think it could well be this species.

SNIG and OBtoW warn that 'northern' Fairy Prion, can approach the head pattern or Slender-billed. I only have one poor photo at a poor angle, which shows the birds upper-parts, but the tail band appears narrow (although perhaps not as narrow as Slender-billed should, which SNIG states has the narrowest tail band).

With prions, it is always possible that you are clutching at straws, but it would be great to know if the smile and bill tip of Salvin's is diagnostic, or whether the thin-billed impression of Slender-billed is truly transient.

That said, if the ID's are ever resolved (and by chance I am right), it will only end in matrimonial angst - I have never knowingly seen Salvin's and I don't think I was with my wife when she took the photos! (Slender-billed we have both seen before - phew!!!).

 

[Paul Chapman]

Hi Paul,

I think they do. I wasn't taking the photographs, but the timing on the full sequence of shots and the position between frames suggest it is the same bird.

The main reference I have used is 'Oceanic Birds of the World' (Steve N.G.Howell & Kirk Zufelt) [OBotW]. I have also referenced 'Seabirds - The New Identification Guide' (Harrison, Perrow and Larsson) [SNIG]. Unfortunately, I cannot easily read the photo you attached, but I think that the OBotW and your paper basically align in that;

Salvin's verses Antarctic

• Antarctic normally shows a bulbous pale nail to the bill, whereas Salvin's shows a darker grey less bulbous nail.
• Salvin's can show a quite pronounced smile line, which seems to be at best is slight and short in Antarctic.
• The bill of Salvin's 'averages' wider and stouter.
• SNIG also suggested Salvin's is 'larger headed with steeper, swollen forehead, larger blue bill and whiter, white cleaner face....'.

In OBotW all of the Salvin's photos show some form of smile line (but this is less distinct in some birds), whereas the Antarctic photos show at best a faint short line (1 in 11 photos). So a big question for me is whether a distinct smile line (and lack of pale bulbous nail), are diagnostic of Salvin's (or Broad-billed).

To eliminate Broad-billed, I think that the bills appear not grotesque enough, and also Broad-billed reportedly has a duskier face with darker lores - Salvin's is stated to have whiter lores - these descriptions are in both OBotW and SNIG.

In my opinion the bird near Macquarie and Enderby seem to be the most interesting - the other bird does seem to show a rather pale nail (but perhaps this is just the light).

Slender-billed verse Antarctic - I don't think this is covered in your paper extract. But my references state

• Slender-billed has a broad-white eyebrow, white lores and narrow dark eyestripe (typically narrower than the supercillum).
• Slender-billed has a narrower and rather slender (but dimensions overlap with some Antarctic Prions).
• Antarctic is also slightly stockier and bigger headed than Slender-billed.
• OBotW states that the forehead is often rather steep and squared in Slender-billed, and that the dark eyestripe is typically narrower than the white brow.

To me the bill is quite odd in Slender-billed - It shouldn't really be called Slender-billed but instead Narrow-billed! In side on photos that I have studied, the bill is not always distinctly shallower that Antarctic - perhaps marginally shallower at the base, and a bit more shapely (less triangular in shape), with more of a step in depth past the nostril and with more of a hook tip. In some photos the bills of Slender-billed look truly 'slender', but I think this depends on the tilt of the head, and whether the 'narrowness' of the bill influences the view. I therefore suspect the impression of the bill can vary when viewing the same bird.

OBtoW warns that Indian Ocean Antarctic can approach the head pattern of Slender-billed, but the only photo they provide is not as clean as the bird my wife photographed.

To me the bird does seem to show the correct head pattern, and does appear slightly smaller headed and less stocky that the accompanying Antarctic - the accompanying Antarctic seems to me to be more bull necked, slightly wider on the hips and perhaps a touch wider winged. The head also seem rather square as suggested by SNIG. This combined with the occasional 'slender-billed impression', still makes me think it could well be this species.

SNIG and OBtoW warn that 'northern' Fairy Prion, can approach the head pattern or Slender-billed. I only have one poor photo at a poor angle, which shows the birds upper-parts, but the tail band appears narrow (although perhaps not as narrow as Slender-billed should, which SNIG states has the narrowest tail band).

With prions, it is always possible that you are clutching at straws, but it would be great to know if the smile and bill tip of Salvin's is diagnostic, or whether the thin-billed impression of Slender-billed is truly transient.

That said, if the ID's are ever resolved (and by chance I am right), it will only end in matrimonial angst - I have never knowingly seen Salvin's and I don't think I was with my wife when she took the photos! (Slender-billed we have both seen before - phew!!!).

Jon

The most important thing in your response is the final paragraph which persuades me that all of your possible Salvin's Prions are Antarctic Prions. 😀

All the best

Paul

 

[Jon.Bryant]

The most important thing in your response is the final paragraph which persuades me that all of your possible Salvin's Prions are Antarctic Prions. 😀

Yes, but if only I could convince myself I saw a Salvin's, I will have seen the lot (I think) and will never have to study another Prion again!

That said OBotW states Antarctic is 'confusingly variable and may habor cryptic species'. 😥

 

[Paul Chapman]

Yes, but if only I could convince myself I saw a Salvin's, I will have seen the lot (I think) and will never have to study another Prion again!

That said OBotW states Antarctic is 'confusingly variable and may habor cryptic species'. 😥

I suspect herein lies the answer... A whole bunch of populations to be isolated, voice recorded & DNA'd! I am interested in the date & time of your possible Slender-billed Prion. I will ask Paul G whether he is happy for me to post his possible Slender-billed pics.

All the best

Paul

 

[Jon.Bryant]

F

I am interested in the date & time of your possible Slender-billed Prion.

Sorry, forgot to mention this - 14 December nearest to the Antipodes.

Cheers

Jon

 

[Paul Chapman]

Sorry, forgot to mention this - 14 December nearest to the Antipodes.

Cheers

Jon

This is the bird that Paul photographed on the morning of 9 December. Facial pattern, bill and upperwing pattern look interesting but tail pattern is maybe less convincing.

All the best

Paul

 

[Jon.Bryant]

As the legendary Peter Harrison was on out trip, I reached out to him for comments on my wife's photographs. He has kindly just responded, and although he understandably caveats his opinions with the comments that Prions and Diving Petrels are the toughest seabird ID challenges, he generally agrees that the photos are of Salvin's and a Slender-billed Prion, with one exception - the bird in the first photograph at the start of this thread (off Macquarie Island) he considers is probably Antarctic Prion, as 'Salvin’s usually shows broader and blunter superciliary, and this bird shows a narrow and pinched superciliary curving over the eye'.

As I think will always be the case with Antarctic and Salvin's, he states the other birds 'appear' to be Salvin's, so no guarantees, but I wasn't expecting any. Even with ultra crisp photos some Prions will always remain an enigma! I appreciate that he made the time to look at the photos, and was willing to voice an opinion, on these ultra tough birds.