G’day all
My friends on the Tanzanian equivalent of birding-aus are currently wrestling with the identification of a frigatebird that has been frequenting some of the nicer beach-side suburbs of Dar es Salaam. They have asked me to post some photos on birding-aus for the Australian experts to examine.
So there are four photos here:
https://www.dropbox.com/sh/bec5nxr4ul166fz/90IJhl3pfU
I’ll pass on any opinions that emerge.
Cheers Steve ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
________________________________ Cc: ‘David James’ Sent: Wednesday, 16 January 2013 10:06 AM
Nikolas, Would you mind expanding on the ‘axillary spur business’ as I’m now thoroughly confused and would have though that this ID could have ruled out Great on the basis of the spurs (hence my confusion). David comments that juvy Greats (when they actually have spurs) have “spurs that originate off the side of the belly patch and extend only onto the flanks, just like this bird.” I am actually seeing the spurs originating from the front of the belly patch, and this combined with the prominence of the spurs and the possibility that they are also just reaching the underwing has me confused – maybe this is what you’re referring to? I’m very happy to concede the subject bird is not an Ascension (and I originally thought Lesser would be a better fit than Greater but I take on board David’s comments there) – moreover I’m curious about your comment on the spurs (i.e. should we not be using them as a reliable character?). Mick
________________________________ Cc: ‘David James’ Sent: Wednesday, 16 January 2013 9:19 AM
Hi all,
I agree with Mike and David that the bird is most likely a Great Frigatebird. Re Mick’s comment: I believe that the ‘axillary spur business’ has caused many Great Frigates on Michaelmas Cay to be misID’d as Lesser Frigates (yes, I know that there are Lesser Frigates, too). Re David’s comment on Magnificent Frigate on Cape Verde: Sadly, to my knowledge, there are only three to six birds left in that relict population.
Cheers,
Nikolas
Hi Mick, Sorry for the delay in replying to you. Perhaps you and Nikolas discussed this further on the pelagic on Saturday. I thought I should clear up some issues you raised that, in my understanding, rule out Lesser rather than Greater Frigatebird. I said I thought the spurs of the Tanzanian bird originated off the sides of the belly patch (consistent with Great). Conversely, you thought they originated off the front of it, which would eliminate Great. I think this comes back to a limitation or interpretation of my descriptions in James 2004. However, there are other ways to word the differences. Bare in mind, that the descriptions of triangles and ovals refer to 2-dimensional shapes, but the under surface of the birds is highly 3-dimensional, so the descriptions are simplifications. In Lesser the margin between the triangular belly patch and the breast band is straight(ish). This line forms the base of the rear-pointing triangular belly patch. This straight line also continues (more or less) to the outer tips of the spurs; no part of the belly patch extends WELL forward of an imaginary line between the points of the two spurs (assuming the angle of view is appropriate). On Great the margin between the oval belly patch and the breast band is rounded, with the convex belly patch intruding into the breast band. The spurs technically cannot originate from the front of the belly patch because the front is confined to the very centre of the chest. I have termed it that they originate from the sides, but technically there are no sides on an oval (well, one side only). In this case, perhaps you could say that the spurs originate from the side between the front and the mid-point of the belly patch. It starts getting a bit grey and murky, and becomes impossible to capture all the variation in a simple sentence. There are some other points that are more important than the origin of the spurs: The shape of the belly patch: The Tanzanian bird has both a rounded front edge and the broadly rounded rear edge creating an oval (if you hide the spurs – colour them in black using a graphics program if you like). Juvenile Lesser always has the belly patch narrowing to a blunt point at the rear. Together with the straight front edge, this makes a distinctly triangular shape, if you cover up the spurs. Actually, however, the spurs tend to add to the triangular shape of the belly patch by stretching out the front (basal) corners. On this particular bird note that the the rear of the belly patch is fairly broad. It is a little bit square at the rear, not perfectly rounded as would be expected in a true ‘oval’. The important detail is that there is a fairly broad separation of the black on the flanks right to the back, rather than a gradually narrowing. The spurs themselves are pointed or triangular on Lesser and blunt-tipped on Great. On Great they are often also jagged. I’ve not looked into why this is, but because each feather is either black or white (no white-tipped feathers) it must be something to do with the shape, size and number of feathers involved). The Tanzanian bird is completely inconsistent with Lesser in this detail. On the Tanzanian bird, it is fair to say that the spurs are longer than normal for a Great Frigatebird, apparently reaching beyond the flanks and onto the axiliaries. Also the spurs originate well forward on the belly patch. These are the only two points that I can construe against Great, and I think they can be explained. I have seen one (almost) definite example of a Great with spurs this long (longer in fact) photographed by Grant Penrhyn at Ashmore Reef in October 2007. It was first thought to be a Lesser, then a CI, but in my view it was a Great. I have a discussion paper on it which I’ll send to you separately. Therefore, if you accept that the Ashmore bird was a Great then the Tanzanian is not unprecedented. This might be a circular argument however. The spurs of the Tanzanian bird might be further forward than usual because we are dealing with a different subspecies to ‘usual’. Subspecies are unfashionable at present in Great Frigatebird, but there is a lot of geographical variation with at least 3 subspecies in the Pacific, 2 or 3 in the Indian and 1 in the Atlantic Oceans. The form in the western IO, ‘aldabrensis’ might have spurs further forward than the forms I’m used to (palmerstoni in the SW Pacific, listeri or nominate minor on CI, and unnamed forms (possibly aldabrensis or minor?) at Asmore and Cocos (Keeling) Islands. But this is speculation. Perhaps it is part of the variation across all subspecies. Overall, frigatebird ID is in it’s infancy, the birds vary greatly, and James (2004) certainly does cover all variation and nail every aspect. You can expect variation. I think the Tanzanian bird just shows that some Greats go a little outside the descriptions in James (2004) that were based on my experience and language limitations at the time.
Cheers, David James Sydney ==============================
________________________________ Cc: ‘David James’ Sent: Wednesday, 16 January 2013 10:06 AM
Nikolas, Would you mind expanding on the ‘axillary spur business’ as I’m now thoroughly confused and would have though that this ID could have ruled out Great on the basis of the spurs (hence my confusion). David comments that juvy Greats (when they actually have spurs) have “spurs that originate off the side of the belly patch and extend only onto the flanks, just like this bird.” I am actually seeing the spurs originating from the front of the belly patch, and this combined with the prominence of the spurs and the possibility that they are also just reaching the underwing has me confused – maybe this is what you’re referring to? I’m very happy to concede the subject bird is not an Ascension (and I originally thought Lesser would be a better fit than Greater but I take on board David’s comments there) – moreover I’m curious about your comment on the spurs (i.e. should we not be using them as a reliable character?). Mick
________________________________ ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================
Hi Mick,
Your description of the spurs was very thorough and, no doubt, the spurs do play a role in the ID of Frigates. However, they can be very confusing, too. What I was trying to say is that this field mark is quite often used too superficially by some observers (obviously not by you, Mick!) to draw a conclusion of the ID. Of importance, as discussed by you, is to age the bird prior to attempting a species ID.
Cheers,
Nikolas
Nikolas, Would you mind expanding on the ‘axillary spur business’ as I’m now thoroughly confused and would have though that this ID could have ruled out Great on the basis of the spurs (hence my confusion). David comments that juvy Greats (when they actually have spurs) have “spurs that originate off the side of the belly patch and extend only onto the flanks, just like this bird.” I am actually seeing the spurs originating from the front of the belly patch, and this combined with the prominence of the spurs and the possibility that they are also just reaching the underwing has me confused – maybe this is what you’re referring to? I’m very happy to concede the subject bird is not an Ascension (and I originally thought Lesser would be a better fit than Greater but I take on board David’s comments there) – moreover I’m curious about your comment on the spurs (i.e. should we not be using them as a reliable character?). Mick
________________________________ Cc: ‘David James’ Sent: Wednesday, 16 January 2013 9:19 AM
Hi all,
I agree with Mike and David that the bird is most likely a Great Frigatebird. Re Mick’s comment: I believe that the ‘axillary spur business’ has caused many Great Frigates on Michaelmas Cay to be misID’d as Lesser Frigates (yes, I know that there are Lesser Frigates, too). Re David’s comment on Magnificent Frigate on Cape Verde: Sadly, to my knowledge, there are only three to six birds left in that relict population.
Cheers,
Nikolas
Hi all,
I agree with Mike and David that the bird is most likely a Great Frigatebird. Re Mick’s comment: I believe that the ‘axillary spur business’ has caused many Great Frigates on Michaelmas Cay to be misID’d as Lesser Frigates (yes, I know that there are Lesser Frigates, too). Re David’s comment on Magnificent Frigate on Cape Verde: Sadly, to my knowledge, there are only three to six birds left in that relict population.
Cheers,
Nikolas
Apologies for the late moderation of this and a few other recent messages, I didn’t get around to checking them between about 5pm yesterday and 7am today. I assume Bill Stent is on his way to Queensland at the moment, so we’re a moderator short at the moment.
Also apologies to “Confused and Frustrated” of Sandstone Point, Qld, for not changing the subject line. Sometimes I think it’s more confusing to change the subject line when the subject changes if it’s still vaguely linked to the original message.
Peter Shute
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================
Mike, Steve et al, I’m not sure if my other post reached the list (it hasn’t hit my inbox), but wouldn’t a sub-adult Great not have any axillary spurs at all? The ones that are on the subject bird are also set a long way forward on the belly patch and are quite prominent, which would rule out Great as well. They actually appear to reach the underwing in some of the images. On plumage I think CI and Lesser the main potential confusion species, but as you say Mike the bill doesn’t look long enough for CI. The belly patch looks the wrong shape for Lesser and it doesn’t seem to “point backwards” on the 4th image, which shows the best view of the bird’s underside…but as I said I think the spurs could actually reach the underwing of the bird. I would be hesitant to use Pizzey as a guide for this (or other young frigates) and I also don’t think we should identify on range either, rather what the bird actually is. Would it be impossible for a bird like that to round the Cape?? 😉 Mick
________________________________ Cc: ‘David James’ Sent: Tuesday, 15 January 2013 1:59 PM
In case he missed this posting, I’ve forwarded this request to David James who knows this group well having lived for three years+ on Christmas Island where all three Australian species breed. David wrote a paper on their ID published in 2004 in BirdingASIA 1, 22-38.
However here are a few comments from me. It is a sub-adult bird but because it appears to have a wholly white head lacking any tawny colouration, it is not a fresh juvenile. The white spurs seem to me to be restricted to the sides of the breast not extending onto the underwing which suggests to me that it is not a Lesser Frigatebird. The bill doesn’t look long enough for a Christmas Frigatebird so assuming that it is of Indian Ocean origin, (Ascension Island is in another ocean without a tropical waters link), my not very confident vote would be for Great Frigatebird.
Mike Carter 30 Canadian Bay Road Mount Eliza VIC 3930 Tel (03) 9787 7136
Thanks for passing this on Mike. I agree with your ID as a Great Frigatebird. Firstly though, frigatebirds disperse widely. Ascension breeds in the Tropical Atlantic, about 6,000 km due west of the coast of Tanzania in the IO. It is a vagrant even to the west coast of Africa, and from there a bird would need to cross tropical Africa or round the Cape to get to Tanzania. It is possible I suppose. Magnificent breeds in the Cape Verde, not much further away, 7,500 km wnw. The same deal applies. Neither has been recorded in the Indian Ocean. Christmas Frigate breeds only on Christmas I in the eastern IO, about 7,300 km east of Tanzania, but there is only tropical ocean in between, no deserts. Christmas has been recorded in Kenya in the 1960s (not officially accepted by Kenya’s rarities committee, but Clive Mann’s photos convinced me and Peter Harrison who originally identified the bird for Clive). On the other hand, both Great and Lesser breed from east to west in the Tropical IO and are regular along the tropical east coast of Africa, so weight of probability is with one of those two. However, all 5 deserve to be considered. I only know Great, Lesser and Christmas well. Steve Howell (1994) dealt with the separation of Great and Magnificent, and I dealt with Christmas, Great and Lesser (James 2004), so Ascension is the only one not treated in a detailed ID article. Frigatebird ID is complicated, so be warned, the following will bore some people to death. The white head indicates it is young but not fresh juvenile plumage. No adult frigatebirds have white heads, not even the pale morph female Ascension (beware of label errors on web photos). The ‘white’ head feathers are worn, abraded and bleached buff feathers of juvenile plumage (Magnificent and Ascension have actual white feathers, and the other 3 bleach to white routinely even before they fledge). The unique brown underparts plumages of Ascension Frigates occur in adult plumages. Breast bands of juveniles of some species have some dark brown mixed with the black, and this is certainly typical of Greater and Lesser, so that in itself is no reason to suspect Ascension. The breast band is narrower in the centre, which creates a rounded anterior edge to the white belly patch, effectively making the belly patch an oval or egg-shape (if you ignore the spurs for a moment). That is the typical shape of a juvenile Great. Lesser has a straight rear margin to the breast band, so a straight anterior margin to the white belly patch, which effectively makes the belly patch more triangular in shape. Photos of juv Ascension on the web appear to show a parallel-sided breast band so a straight anterior edge to the belly patch, but a rounded rear end of the belly patch making it an elongated semi-circular shape. Magnificent has the breast-band narrow and set well back, and sharply tapering to the centre (usually broken across the centre) so the belly patch is small and diamond shaped (Howelll 1994). Christmas has a hexagonal shape to the belly patch with angles rather than curves. The oval belly patch favours Great. The spurs are restricted to the flanks or perhaps just reach the underwing, as Mike observed. They are also blunt-tipped. These eliminate Lesser which has tapering, pointed spurs that extend well onto to the underwing. On Lesser the spurs originate from the front corners of the triangular belly patch. About 1/3 of juvenile Great (although worn this bird still has juvenile body plumage) have spurs that originate off the side of the belly patch and extend only onto the flanks, just like this bird. This bird is admittedly at the extreme end of Great for development of spurs, in my experience. The spurs of Christmas extend well out onto the underwing. Juv Ascension apparently has a lot of white on the flanks, but in the few photos I’ve seen it tends to be broader and more of a flank patch than a narrow spur, though the shape is not consistent. The spurs of Magnificent are small, narrow and tapered (Howelll 1994). The bill of the Tanzania bird is clearly pink. When the adult females have blue bills their juveniles have pale blue-grey rather than pale pink bills. Adult female Ascension and Magnificent have blue bills and the juvs have grey ones. In Christmas the adult female bill is bright pink and the juv is pink. In Lesser the female has pink-billed and blue-billed morphs. In Great the female bill can be pink or blue depending on location. Bill colour rules out Ascension and Magnificent but not Great, Christmas or Lesser. The bill is probably too short for Christmas. The wings are too narrow at the base and the humerals not sufficiently elongate and bulky for Christmas. I think every species can be eliminated on several points, except for Great. It looks absolutely fine for a worn juvenile Great of the Indian Ocean susbspecies aldabrensis (and probably female due to size and pink bill). Howell, S. N. G. (1994) Magnificent and Great Frigatebirds in the Eastern Pacific: A new look at an old problem. Birding Dec. 1994: 400–415. James, D.J. (2004). Identification of Christmas Island, Great and Lesser Frigatebirds. BirdingAsia 1: 22-38. PS Steve, I can provide James 2004 for your drop box if you want Cheers, David James Sydney ============================== ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================
As I said at the beginning, I am no expert on frigatebirds and as the water is getting too deep and treacherous and I might drown I am swimming to shore and will await further deliberations from the experts. I looked at David’s paper and only became more confused.
Greg Dr Greg. P. Clancy Ecologist and Birding-wildlife Guide PO Box 63 Coutts Crossing NSW 2460 0266493153 0429601960
In case he missed this posting, I’ve forwarded this request to David James who knows this group well having lived for three years+ on Christmas Island where all three Australian species breed. David wrote a paper on their ID published in 2004 in BirdingASIA 1, 22-38.
However here are a few comments from me. It is a sub-adult bird but because it appears to have a wholly white head lacking any tawny colouration, it is not a fresh juvenile. The white spurs seem to me to be restricted to the sides of the breast not extending onto the underwing which suggests to me that it is not a Lesser Frigatebird. The bill doesn’t look long enough for a Christmas Frigatebird so assuming that it is of Indian Ocean origin, (Ascension Island is in another ocean without a tropical waters link), my not very confident vote would be for Great Frigatebird.
Mike Carter 30 Canadian Bay Road Mount Eliza VIC 3930 Tel (03) 9787 7136
The brown areas on the chest and flanks of the bird in the photo seem to rule out the other species which don’t seem to have noticeable areas of brown plumage. I am sticking with Ascension Frigatebird.
Greg
Neither am I, but I agree with Greg… in the absence of other theories anyway. The breast band is prominent and wide and the head is white, so it would be a juvenile if it were a Great, Lesser or Christmas. The white belly patch is not elliptical as would be expected on a Great, and the axillary spurs are too large anyway. I don’t think it is triangular either, with it not pointing backwards as might be seen on a Lesser and the spurs start from behind the line of the breast band as well. The axillary spurs are so prominent that it might be tempting to consider a Christmas (and they angle forward and are parallel and are much closer to the front of the wing). But the bill doesn’t appear to be overly long and the prominence of the breast band combined with the very white head leads me away from Christmas. Ascension is the only one I have no experience with, but a quick scan of Google shows that Greg could be on the money. Have a look here, in particular the shape and prominence of the axillary spur on that immature bird at the bottom (not to mention the white head).: http://worldbirdinfo.net/Pages/BirdMediaView.aspx?BirdID=31526&Source=%2FPages%2FBirdsSearch.aspx%3FBirdField%3D8%26BirdSearch%3DFREGATIDAE%253AFrigatebirds By the way, I can’t recommend enough the paper by David James on Frigatebird ID (especially if you’re visiting Christmas Island!). Mick
________________________________ Sent: Tuesday, 15 January 2013 12:05 PM
I am not an expert on Frigatebirds but the closest I can find in my copy of Handbook of the Birds of the World is the Ascension Frigatebird, a young or pale morph bird.
Greg
Dr Greg. P. Clancy Ecologist and Birding-wildlife Guide PO Box 63 Coutts Crossing NSW 2460 0266493153 0429601960
Hello Steve. Juvenile/immature Frigatebirds are notoriously difficult to separate, but the white around the armpits leading into the wings suggests Lesser Frigatebird to me. I think Ascension Frigatebird would be well out of range. According to Pizzey and Knight, Juvenile Great Frigatebirds are “not safely separated” from other Frigatebirds. Cheers Steve Murray
I am not an expert on Frigatebirds but the closest I can find in my copy of Handbook of the Birds of the World is the Ascension Frigatebird, a young or pale morph bird.
Greg
Dr Greg. P. Clancy Ecologist and Birding-wildlife Guide PO Box 63 Coutts Crossing NSW 2460 0266493153 0429601960