Hi All,
This afternoon at Windang, south of Wollongong, a combined outing of Cumberland Bird Observers Club and Illawarra Birders Inc saw a very exhausted-looking large seabird on the northern sea wall. It appears to be a Jaeger but what species? The link is http://www.flickr.com/photos/martinpott/6409919231/ Any help much appreciated! Thanks,
Martin Potter Illawarra Birders Inc
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Hi all, Marie Lister has sent me some more photos of the Windang skua, including dorsal and ventral shots in flight. It now appears to be certainly an Arctic (too many primaries with white bases and shafts for Long-tailed, to gracile for Pomarine, plus bicoloured bill). It is also an adult, because it has entirely uniform underwing coverts. It is also in heavy moult, replacing very worn and bleached feathers all over, showing a big hole in the middle of the tail, most secondaries replaced but outers still growing, some inner primaries new and a dogs breakfast in the coverts. Contra my previous post, it appears to be only 2 generations of feathers, but an unusually long time since the last one. So Nikolas was right from the outset, and Jeff was on the ball that pale fringes to the upperparts are actually a feature of winter plumage in Arctic Jaegers of all ages. Very educational for me. Thanks everyone for sharing the photos and your insights. I’ll forward the photos on to those involved (in case I’m still wrong).
David James, Sydney burunglaut07@yahoo.com ==============================
________________________________ Cc: ‘Martin Cocker’ Sent: Monday, 28 November 2011 12:48 PM
G’day Dave,
I really wonder sometimes about the fresh white fringed back feathers as indicating immaturity. I now have lots of photos of birds showing this with strong dark bars forming the breast band, but combined with unambiguously completely dark under-wing coverts, eg adult or certainly well past 2nd year, but have no photos of winter adults from Australia for this time of year not showing it, have the books definitely got this right?. I would also suggest that the dorsal primaries base wing flash is not visible on the folded wing because the outer vein of each flight feather overlaps the white shaft of the underlying feather in each case. It’s really important that if anyone managed photos of this bird showing the under-wing that they share them with us to assist sorting out Jaegers on the wintering grounds. I see the lack of wing moult as the most interesting aspect of this bird, but I’m not sure whether it ages the bird or not.
Cheers Jeff.
Whoops, sent that to early. It still appears to be showing 3 generations of feathers. That is something that is rarely if ever possible unless one of the generations is juvenile. Perhaps it is also possible in a sick adult that suspended a complete moult some time ago??? David James, Sydney burunglaut07@yahoo.com ==============================
________________________________ Cc: ‘Martin Cocker’ Sent: Monday, 28 November 2011 1:20 PM
Actually, I think you are right Jeff. I’ve just gone to BWP where C.S. Roselaar wrote the jaeger plumages (and he didn’t get much wrong). It does indeed say for adult non-breeding light morph that “Hindneck and mantle barred and fringed pale buff-grey”. The barring maybe is a winter trait, not an immature trait. Perhaps subsequent texts misread that? I wonder if the lack of wing moult can help, if the bird was sick and dying. In the NMNZ there are a bunch of specimens of Long-tailed Jaeger that all wrecked in NZ, perhaps in the late 70’s. None of them had moulted and their primaries were worn to shafts and like straws. I suppose they did not have enough food (energy) to moult so kept the old feathers way past the use-by date and eventually could no longer forage. So I’d be wary of placing strict reliance on moult to age an unhealthy jaeger. David James, Sydney burunglaut07@yahoo.com ==============================
________________________________ Cc: ‘Martin Cocker’ Sent: Monday, 28 November 2011 12:48 PM
G’day Dave,
I really wonder sometimes about the fresh white fringed back feathers as indicating immaturity. I now have lots of photos of birds showing this with strong dark bars forming the breast band, but combined with unambiguously completely dark under-wing coverts, eg adult or certainly well past 2nd year, but have no photos of winter adults from Australia for this time of year not showing it, have the books definitely got this right?. I would also suggest that the dorsal primaries base wing flash is not visible on the folded wing because the outer vein of each flight feather overlaps the white shaft of the underlying feather in each case. It’s really important that if anyone managed photos of this bird showing the under-wing that they share them with us to assist sorting out Jaegers on the wintering grounds. I see the lack of wing moult as the most interesting aspect of this bird, but I’m not sure whether it ages the bird or not.
Cheers Jeff.
Actually, I think you are right Jeff. I’ve just gone to BWP where C.S. Roselaar wrote the jaeger plumages (and he didn’t get much wrong). It does indeed say for adult non-breeding light morph that “Hindneck and mantle barred and fringed pale buff-grey”. The barring maybe is a winter trait, not an immature trait. Perhaps subsequent texts misread that? I wonder if the lack of wing moult can help, if the bird was sick and dying. In the NMNZ there are a bunch of specimens of Long-tailed Jaeger that all wrecked in NZ, perhaps in the late 70’s. None of them had moulted and their primaries were worn to shafts and like straws. I suppose they did not have enough food (energy) to moult so kept the old feathers way past the use-by date and eventually could no longer forage. So I’d be wary of placing strict reliance on moult to age an unhealthy jaeger. David James, Sydney burunglaut07@yahoo.com ==============================
________________________________ Cc: ‘Martin Cocker’ Sent: Monday, 28 November 2011 12:48 PM
G’day Dave,
I really wonder sometimes about the fresh white fringed back feathers as indicating immaturity. I now have lots of photos of birds showing this with strong dark bars forming the breast band, but combined with unambiguously completely dark under-wing coverts, eg adult or certainly well past 2nd year, but have no photos of winter adults from Australia for this time of year not showing it, have the books definitely got this right?. I would also suggest that the dorsal primaries base wing flash is not visible on the folded wing because the outer vein of each flight feather overlaps the white shaft of the underlying feather in each case. It’s really important that if anyone managed photos of this bird showing the under-wing that they share them with us to assist sorting out Jaegers on the wintering grounds. I see the lack of wing moult as the most interesting aspect of this bird, but I’m not sure whether it ages the bird or not.
Cheers Jeff.
G’day Dave,
I really wonder sometimes about the fresh white fringed back feathers as indicating immaturity. I now have lots of photos of birds showing this with strong dark bars forming the breast band, but combined with unambiguously completely dark under-wing coverts, eg adult or certainly well past 2nd year, but have no photos of winter adults from Australia for this time of year not showing it, have the books definitely got this right?. I would also suggest that the dorsal primaries base wing flash is not visible on the folded wing because the outer vein of each flight feather overlaps the white shaft of the underlying feather in each case. It’s really important that if anyone managed photos of this bird showing the under-wing that they share them with us to assist sorting out Jaegers on the wintering grounds. I see the lack of wing moult as the most interesting aspect of this bird, but I’m not sure whether it ages the bird or not.
Cheers Jeff.
Regarding white chevrons in the primaries of juvenile Arctic Jaegers, Olsen & Larsson 1997 state on p.131, (character number 9 of 13) ‘Primaries have narrow, but distinct pale tips, diagnostic when arranged as arrowhead marks (similar to pattern on adult gulls): a good character on settled birds, but visible also in flight at very close range’. I agree though that in this bird those pale edges could be produced by bleaching not just wear.
Mike Carter 30 Canadian Bay Road Mount Eliza VIC 3930 Tel (03) 9787 7136
Hi David, Mike et al,
Yes, I spoke too soon. I agree with both of you that it is a second year pale morph Arctic Jaeger. (Further reasons for it not being a Long-tailed Jaeger: the bill appears too long and the head not round enough)
Cheers,
Nikolas
I tend to agree with Nikolas that it is an Arctic, although I haven’t any experience judging the amount of white wing flash in the folded wing of standing jaegers. I definitely agreewith Mike that it is not an adult. Although the resolution is not great, it appears that the wing coverts and flight feathers are very worn. Conversely, the mantle feathers are a mix of worn and new feathers. The new feathers are darker with narrow white fringes. These are not retained juvenile feathers they are new feathers. They are not adult feathers because the white fringes are an immature trait that occur in juvenile, 1st and supposedly some 2nd yr birds. Looks like some of the median coverts and the remainder of the mantle are newer than the primaries but older than the freshest mantle feathers. My interpretation is that the primaries, secondaries, greater coverts and tail are retained and worn juvenile feathers, the worn head and body feathers and median coverts are 1st winter/summer, and the new mantle feathers are 2nd winter. The bird must have hatched in mid 2009, as Mike determined. Mike, I hadn’t notice the statement in Malling Olsen & Larsson that white tips to juvenile primaries are diagnostic of Arctic. It’s a little hard to make out, but the last photo in that book is a juv Long-tailed with white tips to the primaries. In the Windang bird I think the retained primaries are too worn and bleached to have retained any original white-tips. If there is a faint impression of pale tips it may be due to fraying and bleaching of the tips.
David James, Sydney burunglaut07@yahoo.com ==============================
________________________________ Cc: Martin Cocker Sent: Sunday, 27 November 2011 11:08 PM
I agree with Nikolas that this is a pale morph Jaeger in very worn plumage, definitely not a Pomarine Jaeger, most probably an Arctic Jaeger rather than a Long-tailed (because of the pale blaze – but there is only a small amount of white at the base of the primaries which leaves me a little unsure). However, I have more of a problem accepting that it is an adult as the white spots on the mantle look to be remnants of juvenile barring the presence of which I can’t explain in an adult. Perhaps Nikolas or others can. Therefore I would be happier considering this to be an 18 month old bird in second winter plumage, two or three years short of a full adult. But another perhaps age related feature is the white tips to the primaries. When in juveniles these white tips form a series of chevrons they are said to be diagnostic of Arctic Jaeger (Olsen & Larsson 1997). Jaegers are notoriously difficult to ID and photographs of open wings particularly underwings are very helpful in this process.
Mike Carter 30 Canadian Bay Road Mount Eliza VIC 3930 Tel (03) 9787 7136
One never stops learning….listen and learn, always!! Thanks Nikolas and Mike. Peter
I agree with Nikolas that this is a pale morph Jaeger in very worn plumage, definitely not a Pomarine Jaeger, most probably an Arctic Jaeger rather than a Long-tailed (because of the pale blaze – but there is only a small amount of white at the base of the primaries which leaves me a little unsure). However, I have more of a problem accepting that it is an adult as the white spots on the mantle look to be remnants of juvenile barring the presence of which I can’t explain in an adult. Perhaps Nikolas or others can. Therefore I would be happier considering this to be an 18 month old bird in second winter plumage, two or three years short of a full adult. But another perhaps age related feature is the white tips to the primaries. When in juveniles these white tips form a series of chevrons they are said to be diagnostic of Arctic Jaeger (Olsen & Larsson 1997). Jaegers are notoriously difficult to ID and photographs of open wings particularly underwings are very helpful in this process.
Mike Carter 30 Canadian Bay Road Mount Eliza VIC 3930 Tel (03) 9787 7136
Non-breeding adult pale morph Arctic Jaegerin my opinion. Told by overall slender jizz (as opposed to skua-like heavy-chested appearance of Pom), the slender, uniformly colored bill (as opposed to thick and bicolored in Pom), the very worn plumage (ad) and finally the overall coloration (non-breeding pale morph).
Cheers,
Nikolas
Hi there,
Looks like a Pomarine Jaeger to me, plumage and size……but, size can be so subjective. Anyone? Cheers Peter Madvig