A blog mainly about birds and birding, to supplement my website I shall add new posts on an ad hoc basis as and when I have something I think is worth sharing, whether that’s an interesting bird, something I’ve learned, perhaps about identification, or something that’s aroused my curiosity. Often there will be questions, some of which you might be able to answer... please use the comments!

Tuesday, 5 April 2016

More white-headed intersex Wigeon weirdness

To set the context I've been interested in Wigeon with white on the head for a while, having noticed several females in different places showing patches of white behind the eye.  I blogged about this in early 2014, questioning why this apparent leucism should occur at a relatively high frequency behind the eye rather than anywhere else.  I noticed a similar phenomen with Brent Geese which fairly often show white speckling on the head but very rarely show abnormal white feathering elsewhere.

Wigeon, Buckenham, 25th January 2014

Wigeon, Caerlaverock, 29th December 2005

Then when I saw the same white-headed Wigeon at Salthouse over the course of several winters it dawned on me that my initial identification of it as being a first-winter male could not have been correct - it can't still be a first-winter male!  Its mixture of male and female features retained over at least 4 winters must surely mean it has gender issues, presumably an intersex bird.  I blogged about that at the end of last year.

Wigeon, Satlhouse, 1st December 2012

same Wigeon, Satlhouse, 23rd December 2015

Well on Saturday things took a bizarre twist.  I found another Wigeon with white behind the eye - quite a lot in fact - more than any of the previous birds.  And what was really weird is that it seemed to show a mixture of male and female features, though was predominantly female.  I think the clear-cut white-edged wing-coverts and late date for a predominantly female-like bird mean that it cannot be a first-winter male, so it would appear that it was another intersex bird.

Wigeon, Burnham Norton, 2nd April 2016

Now, in the photos the evidence of masculinity is sparser than I'd thought while I was watching it.  But I think it's there.  I don't think an ordinary female would show so much black around the tail with contrasting whitish area in front, the scapulars are perhaps a tad long and grey (?) and there seems to be a slight hint of the cream forehead showing through.  Maybe that's not entirely convincing - perhaps I should not say definitively that this bird is intersex, but it seemed that way in the field and it certainly doesn't look typical for a female.

One feature that is atypical for either gender is the dark barring on the breast and flanks.  Now it may be a coincidence (but I doubt it) but intersex Pintails seem to show dark vaguely similar dark barring on the flanks that is not present (in the same form) in normal male or female Pintail.  The Salthouse Wigeon shows a bit of this too, mainly on the breast.

So if this is an intersex bird, what are the odds of two intersex Wigeons both having white on the head if that white is simply random appearance of leucism?  Surely impossibly low?  So that would suggest that the white on the head is somehow linked to the birds' abnormal gender.  Why on earth should that be so?

If it is so, it made me wonder if ALL the Wigeons I've seen with white behind the eye might be intersex?  Most have been females, which is fine.  Intersex birds seem to be females that develop male characteristics over time, so we might expect many to still resemble females externally.  Only two were initially identified as males, the Saltouse bird that turned out to be intersex when it reappeared in subsequent winters, and one from Buckenham in 2014.  Here's the Buckenham bird... check out the breast!

Wigeon, Buckenham, 25th January 2014

This bird shows little sign of being a female - it's plumage is fully male.  But what's with those dark markings on the breast?  They aren't exactly normal for male Wigeon.  I noticed that at the time but had no explanation.  Now I can't help noticing the similarity with the dark markings on the Burnham Norton bird's breast and the Salthouse bird's breast.

So the question is, can pigment deficiency conditions like leucism be linked to gender abnormality?  And why?

And what about those Brent Geese - are they all intersex too?

Dark-bellied Brent Goose, Salthouse, 18th January 2004

Or is it just a coincidence?  Or is there another explanation I've missed?  Let me know what you think.

Wednesday, 23 December 2015

Intersex Wigeon?

I have seen a number of female Wigeons showing white behind the eye and when I found a first-winter male with white behind the eye at Salthouse in December 2012 I assumed I was seeing the same phenomenon again.  I thought it was coincidence when I saw a similar first-winter male in the same spot in February 2014 but when I heard it was back in late 2015 I realised they all had to be the same bird.  Not only were they all very similar, clearly aberrant, birds but they were in precisely the same spot, away from the main flock of Wigeon that winter at this site.  They have to be the same bird, and if they're the same bird then it can't (still) be a first-winter!

Wigeon, Salthouse (Norfolk, UK), 22nd February 2014

Wigeon, Salthouse (Norfolk, UK), 1st December 2012

Wigeon, Salthouse (Norfolk, UK), 23rd December 2015

So what is it, if not a first-winter male?  I missed a clue from the start that this wasn't a first-winter, I think.  The wing-coverts have - and have had since I first saw it - clear whitish fringes.  I believe first-winters should have browner fringes, less clear-cut than these.  It can't be an adult male with these non-white wing-coverts, so it must be an adult female.  But it has male-like grey feathers coming through on the scapulars and flanks, and the head is more solid reddish brown than I would expect on a female.  I think there's even a hint of the cream crown - just faint, but looking rather like it can on first-winter males where it's just beginning to come through.  In fact the pattern of grey male-like feathers does make it look a lot like a first-winter male - it wasn't completely stupid of me to jump to that conclusion when I first saw it!  Here's a first-winter male (already with white wing-coverts) that looks fairly similar:

first-winter male Wigeon, Horsey (Norfolk, UK), 17th December 2011

So the Salthouse bird is an adult female with some male features - an intersex, presumably.  But I had the impression that intersex birds develop over time, becoming more male-like as time goes on.  This bird is no more male-like now than it was four winters ago, so that seems surprising if it is an intersex - but what other explanation can there be?  Do some intersex birds only ever go so far towards male-like plumage?

Closer inspection reveals some other features that don't seem quite normal on male or female Wigeon.  The extent of dark barring on the breast is greater than I would expect, though this is normally variable on Wigoon.  There's also a bit of dark barring on the fore-flanks.  Maybe these are features thrown up by intersex Wigeons?  There is precedent for that happening with intersex ducks - intersex Pintail can show dark barring on the flanks, unlike any normal plumage of Pintail (eclipse male comes closest).

And the white on the head?  Is it too big a coincidence that one bird should show two different abnormal conditions (leucism as well as intersex)?  Probably not - intersex birds seem to be more prevalent among birds already suffering from some kind of abnormality, e.g. in hybrids or selectively-bred mutants.

If this is a female developing male characteristics, are we right in calling it intersex?  Or are there other conditions that lead to the same phenotypic outcome?

Thursday, 26 March 2015

Brown-bristled Marsh Tits?

A recent post on BirdForum drew attention to a new feature for separating Marsh Tits and Willow Tits.  The claim is that Marsh Tits always have black nasal bristles whereas Willow Tits have brown nasal bristles once they mature (young birds may have black nasal bristles like Marsh Tits).  See posts #10 & #11 on this thread.

On Saturday I had the opportunity to watch and photograph several Marsh Tits coming down to seed at Lynford Arboretum.  Lynford has certainly hosted Willow Tits in the past and is not far from where Willow Tits continue to persist, but whether any recent claims of Willow Tit there have been reliable or not, I am not sure.  While I was watching I didn't see anything that made me suspect Willow Tit.  When I used to see both species regularly I found the bull-necked appearance of Willow Tit to be pretty reliable and quite different from the more delicate and elegant Marsh Tit (at least more reliable than the recent literature suggests it should be - but I do agree with these papers in so far as it's a subjective feature so easy to misapply, especially if identifying from photos).  Another feature that's dissed in recent literature is the wing-panel.  Well rightly so as there's huge overlap, but then again I wonder if birds at the extremes might be identifiable on that feature alone?  Anyway, I digress - my point is that all the birds I saw looked like Marsh Tits.  Many of them called and I definitely only heard Marsh Tits.  I suppose it's not impossible that a Willow Tit sneaked in without calling while I was looking through the camera lens rather than paying attention to what the bird looked like, but I doubt it.

These are some of my pics:

Marsh Tits, Lynford Arboretum (Norfolk, UK), 21st March

Some of these birds seem to have black nasal bristles, like they're supposed to.  But a couple of them seem to have at least a slightly brownish tone to the nasal bristles.  It's very subtle, but I don't think it's just my imagination - can you see the brown in these?

Marsh Tits, Lynford Arboretum (Norfolk, UK), 21st March

The first of these two is a tight crop of the second photo above.  The pale spot on the mandible isn't obvious in this photo but it is in the other photos of the same bird (including the top photo of the six above).  In any case it looks like a pretty standard Marsh Tit and doesn't have anything to make me think it might be a Willow Tit.  The second is a tight crop of the fifth photo in the set above (same bird in the fourth photo too).  That bird does look a bit more Willowy in the photos, structurally, but I didn't pick that up in the field.  It also shows a clear and strong pale mark at the base of the upper mandible which, while not held out to be 100% reliable, is surely a pretty clear pointer to this being a Marsh Tit.

Now I don't think the brown tones on my birds here are as strong and clear as they are in Ashley's photos of brown-bristled Willow Tits on BirdForum.  But to my eyes there's a clear contrast between the slightly brownish bristles and the blacker forehead and crown, especially on the lower photo.

What does this mean?  Four possibilities so far as I can see:
  1. Brown bristles on a Marsh/Willow Tit is not a reliable means of identifying it as Willow Tits, contrary to Ashley's claim on BirdForum.  I know Ashley is experienced with both species but I don't know how extensive his data is on which he has based this claim.
  2. It IS a good feature but instead of saying black for Marsh Tit we should say black or blackish brown - as distinct from the more clearly brown of Willow Tit.
  3. It is a good feature but can be misleading in photos.  Mine aren't of the finest quality and some colour aberration in the photo may have contributed to a more brownish appearance, which is more evident in the bristles which were a subtly different shade of black.  Not convinced, but I throw it out as someone might want to make the case for it.
  4. My birds are Willow Tits.  I'm sure they're not, but I'm capable of being wrong.
  5. My birds are hybrids.  Being a hybrid nut I like this idea, but I don't seriously think it's likely.  Worth thinking about though, especially if the evidence for Ashley's claim is robust and black really does mean black, as opposed to blackish brown. 
There may be other possibilities - let me know if you think so.

If possibilities 2 or 3 are the explanation then this has implications for how we should apply Ashley's new feature, and clearly considerable care is required (and much more so if possibility 1 is the answer).  I am personally content to rule out possibility 4.  I think we need more understanding before embarking too strongly on the hybrid theory, though I would point out that (a) hybridisation between these two species has been reported, and is very likely to be overlooked when it does occur so can be expected to be massively under-reported; (b) hybridisation between other Poecile species (e.g. in North America) occurs quite frequently and (c) hybridisation is most likely in places where one species is either spreading into an area already occupied by the other (not relevant here) but perhaps also where one species is withdrawing from an area still occupied by the other (possibly very relevant here).

What do you think?

Thursday, 22 January 2015

Brood manangement of Hen Harriers: working with or working against?

A slight diversion from the stuff I usually blog about.  This post has nothing to do with identifying birds or how birds appear.  It has to do with conservation, and how different approaches to conservation work together - or not.

Here's the thing.  There's always been a tension between the conservation and birding communities and the shooting and gamekeepering communities.  One view from conservationists is that they should work with and influence shooting/gamekeepering communities, another is that they should fight against them.  I'm not sure what the right answer is, but what I see happening this morning is definitely not the right answer.  What I see this morning is conservationists who want to fight against shooters fighting against conservationists who want to influence shooters.

In the good old days I was under the impression that most conservationists and conservation bodies (like the RSPB) took the approach that while they didn't really like people shooting grouse, they recognised that the people who shot grouse maintained grouse moors, and that was prerequisite for grouse to survive - and that in turn allowed their predators to survive.  I thought the thinking was that if you stop grouse shooting you stop grouse moor maintenance resulting in loss of grouse habitat, loss of grouse and loss of harriers.  Maybe that wasn't the official stance - maybe it was just what a few people I mixed with told me, but it was the view I was exposed to when I was growing up and I bought the argument - it made sense to me.  And I thought conservation bodies like the RSPB were seeking to work with landowners and gamekeepers and the shooting community in general.  It was a fragile relationship for sure, but one they thought was worth persisting with.

Red Grouse, Cumbria/Co Durham border, 30th December 2011

Only in recent years has the tide of opinion seemed to change.  Recently the overwhelming majority view that I'm exposed to is that there is no working with the shooting community.  They are all bad, through to the core.  And now the popular approach for conservationists is to aggressively and activley oppose the shooting community and to campaign against grouse shooting in particular.

If I've read things right, many conservationists have decided that they've spent enough time and effort trying to partner with the shooting community and gamekeepers and have become so frustrated that their efforts have come to nought that they've given up that approach and switched to a new one.  It's the opposite to "if you can't beat them, join them": it's a case of joining with them isn't working so we'll beat them instead.

I don't know what the right answer is.  Breeding Hen Harriers have been all but wiped out in England and the shooting and gamekeepering community continue to spout utter nonsense in support of killing raptors.  The notion that a healthy population of predators can decimate  whole populations of their prey and remain healthy themselves, and that killing predators will somehow save our songbirds is as absurd as anything I can imagine, yet it is promulgated endlessly by gamekeepers and shooters.  Gamekeepers are being prosecuted and found guilty of killing raptors and their communities denounce their crimes in the most thinly veiled supportive way they think they can get away with.  I can certainly understand why conservationists have lost patience with them and switched to outright opposition.  Is there any point in persisting with a collaborative approach?

It seems that the Hawk and Owl Trust think there is.  They're supporting a proposal to allow brood management of Hen Harriers under certain conditions which, they believe, will offer sufficient benefit to Hen Harrier conservation that it will outweigh any disbenefit of brood management.  Brood management means that if two broods of Hen Harriers hatch within specific proximity of each other the second brood is removed and raised in an aviary before being released in suitable habitat after fledging.  One condition is that all remaining chicks must be satellite tagged which (a) allows monitoring and (b) deters shooting.  The other conditon is basically that members of the gamekeeper organisations behave themselves.  You can read about it here.  I don't honestly know if it is a good idea or a bad idea, but it doesn't seem unreasonable.  More to the point, it seems that it was a thoroughly and properly considered idea that is intended to support Hen Harrier conservation.

Hen Harrier, Sheringham, 29th October 2011

Mark Avery is now a prominent figure in conservation.  He worked for the RSPB for 25 years and for most of that time was the RSPB's Conservation Director.  Maybe it's just because of the advent of social media, but he seems to me to have come to greater prominence since leaving the RSPB four years ago.  I only started to become aware of him towards the end of his time at the RSPB when I became increasingly concerned about some specific conservation policies that the RSPB were adopting under his leadership (particularly their partnership in the misguided and thankfully now abandoned project to introduce White-tailed Eagles into East Anglia).  I don't remember seeing it when he was still at the RSPB and maybe his independence has given him the freedom to be more public about what he really thinks, but new or not he is now pretty vocal in his opposition to the shooting community.  Maybe I just missed it before - I never found the RSPB magazine a great read (that's not a criticism - I support it targeting people who aren't already dedicated birders) and Twitter didn't exist, but now at least his approach seems to be an all out war, burn the bridges and don't even think about partnership or collaboration.  He gets a lot of support for that approach and with patience with the shooting community at an all time low it's little wonder he does.

Mark Avery may have done a lot of good and much of what he says and does may be of real benefit to conservation.  He may deserve the prominence and support that he enjoys and maybe he even deserve a knighthood as I saw someone suggesting recently.  But I don't think he deserves it for his blog post this morning.  In it he attacks the Hawk and Owl Trust for their stance on brood management of Hen Harriers.  He doesn't simply argue against their stance (I wouldn't mind that but he doesn't even do that very persuasively) but he attacks the trust.  Because the trust have a different more collaborative approach then he does they must be on the shooters' side.  Or on the landowners' side as he characterises that (not entirely without justification, I suspect, but unhelpfully here).  Their chairman might be a landowner but maybe that's a positive not a negative.  Maybe that gives them an opportunity to influence landowners in a way that promotes conservation far more effectively than burning bridges and trying to destroy them.

Just to remind you, according to their submission to the Charity Commission, the Hawk and Owl Trust "works to conserve wild bird of prey and their habitats and to encourage people to enjoy and understand these special birds.  It carries out its objectives through creative conservation, practical research and imaginative education."  From what I've seen of them at Sculthorpe Moor that sounds about accurate.

I don't know which approach to conservation is the right approach.  I don't know if we're best off attacking the shooting community or finding common ground and influencing them.  But I'm pretty sure that conservationists attacking conservationists isn't the right approach.

Saturday, 25 October 2014

A gull

I hold my hands up and admit I'm not very good with gulls.  I know a lot of birders would say the same, but while some give up on them and others love them, I look at them but feel like I'm no better at identifying them than I would be if I'd given up on them.

Gull sp., Cosmeston Lakes Country Park (Glamorgan, Wales), 23rd February 2012

Anyway, here's a gull I can't identify.  I did identify it at the time, but I think I made a mistake.  I thought it was a Lesser Black-backed Gull.  Can't remember why, but I'm guessing it was at because it shows dark flight feathers lacking paler inner primaries and because there are dark grey feathers in the mantle.  Surely that's enough to rule out Herring Gull?  I may have thought that the solidly dark tertials with whitish tips pointed the same way, but they're worn and a quick check of images of 2CY Herring Gulls in February finds several similar.

Now I'm going through all my Lesser Black-backed Gull images for my website and apart from the fact that the scapulars look pretty pale the thing that's really alarming me for an ID of Lesser Black-back is the greater coverts.  Can a Lesser Black-back really show greater coverts like that?  They look more Herring Gull to me.  And the tail - isn't that more Herring Gull like?  The rump certainly isn't white - shouldn't it be if it was Lesser Black-back?

I am wondering about Yellow-legged Gull.  I don't expect them to look like this, but it's an idea that seems to have some merit.  I hardly ever pick out young Yellow-legged Gulls whereas I find quite a good number of adults and older immatures.  I think this is because I don't know enough about plumages of younger Yellow-legged Gulls and I'm overlooking them.  Have I overlooked one here?

In this link there's a second calendar-year Yellow-legged Gull in February that looks a lot like my bird.  It's not the same, but the scapulars and the wing-coverts are pretty close.  The dark flight feathers are better for Yellow-legged than for Herring, and the marked rump is better for Yellow-legged than for Lesser Black-backed - or at least I think so.

So is this a Yellow-legged Gull?  Please comment and let me know what you think - and why.

Gull sp., Cosmeston Lakes Country Park (Glamorgan, Wales), 23rd February 2012

Sunday, 28 September 2014

Common Tern - from east or west?

Common Tern, Burnham Overy, 20th September 2014

Well the Lesser Whitethroat may not have made the grade, but what about this Common Tern?

Since 2011 there have been a number of reports of Common Tern showing characteristics of the eastern form longipennis.  Possibly all reports in Suffolk and Norfolk relate to a single individual.  In May 2014 one was photographed at Scolt Head and in August it was seen at Cley.  I gather it had summered on Scolt Head, though I'm not clear how often it was seen there.  Knowing only of the Cley reports, and not realising it had summered at Scolt, I was not expecting to see it when I visited Burnham Overy in August.  On 25th August I picked up a tern on the far side of the channel that divides Gun Hill from Scolt Head and which, momentarily, I thought was going to be a moulting adult Black Tern, or even a Whiskered Tern.  Quickly I determined it was no marsh tern but an odd Common Tern, and then thoughts of Eastern longipennis entered my head.  It showed a fully black cap, unlike other Common Terns present, and a dark bill.  Together with the darker plumage, especially on the underparts, I wondered if this could be the Eastern Common Tern from Cley.  I'd seen photos of that bird, and I recalled the grey underparts being fairly even, but this bird looked almost patchy - or at least it was distinctly darker around the mid-rear flanks and centre of the belly, and the dark colour seemed to extend on to the underwing which I'd not remembered was the case on longipennis.  Perhaps if I'd realised the Eastern Common Tern had spent most of its time in this area and was only visiting Cley from here, I'd have reached a different conclusion, but I didn't realise that, and the odd pattern of the darker colour made me dismiss it as an odd dark-billed late-moulting Common Tern, probably contaminated to make its plumage look dark.  In any case it was a long way off and before I could get anywhere near it a dogwalker had flushed it right off.  I didn't really have an opportunity to fully resolve it, but didn't particularly suspect that I'd been watching anything rare.

News that the Eastern Common Tern was at Scolt a few days later made me think again, especially when I learned it had probably been there all along, and had just started commuting to Cley each day.  Suddenly it didn't seem unlikely that it would be visible from Burnham Overy.  Maybe my bird had been that after all?  I would never know for sure unless I saw it again, and on 18th September I did - or at least I might have done.

This time it was in the same place, asleep with Sandwich Terns and this time the only Common Tern present.  It looked dark - not just because it was with Sandwich Terns, at least I didn't think so, but I couldn't see the underparts clearly because of the angle it was facing.  I couldn't see its bill (tucked in) but from what I could see of the head it seemed to have a full clean black cap.  It was a long way off again though, and I couldn't get anything more on it.  Once again a dogwalker flushed the whole flock, but unfortunately chose to do so when I was momentarily distracted by a Redstart popping up next to me.  I didn't see it get up and fly off, and I couldn't relocate it.

No sign next day but on 20th there were 3 Common Terns there.  One of them (the only adult) looked interesting but it was sooo far off neither I nor the other birders I'd put on it could resolve it.  It looked dark (above as well as below), the bill looked black, the cap looked full and the legs looked diddly short, but it was impossible from this far off.  I headed off down the beach taking care not to flush it and eventually got a reasonably good look.  From closer I could confirm that the underparts were indeed grey, darker than I would expect on a Common Tern, but that this did not seem to extend far up to the head which I would have expected on longipennis.  Interestingly the grey did appear darkest in the places where the bird on 25th August had looked dark - I think that may well have been the same bird and the dark wasn't down to contamination!  It looked darker from above too, and on the underwing.  The bill was very nearly black, but in a good view you could see it was actually very dark blackish red.  As for the structure of the bill, I'll leave you to judge from the photos - I struggle with that sort of thing, especially as there were no adult Common Terns for comparison.  It wasn't in full summer plumage after all - the forehead was white, though I didn't think it was so extensively white as on some of the Common Terns I was seeing weeks ago.  There was some smudge of black running below the cap on to the cheek - I'd heard the Eastern Common Tern was very cleanly-marked, so was this an issue?  Structurally it looked sleek and elegant - long-winged, but was I sure it was too much for a normal Common Tern?  Not sure, no.  There was nothing to make me think it definitely wasn't the Eastern bird, but enough to make me doubt it - I certainly wasn't going to start claiming it as such until I'd done a good deal more research.

Now I've looked into things a bit more I still don't have a final answer.  Lots of questions though!

  • The bill being slightly red, though only really discernible reasonably close, is fine for longipennis, though I am less clear whether or not it matches the Norfolk longipennis. Of course western Common Tern shows a dark bill in winter, and one unresolved question for me is how (ab)normal would it be for an adult hirundo to have such a dark bill at this time of year?

  • The bill showed a tiny pale tip at close range.  I know this is normal on summer hirundo Common Terns and it seems to be present on photos of longipennis too.  But is it present on winter hirundo too?  Not visible on at least some photos of winter hirundo but I don't have much experience in winter.  If it does normally disappear as the bill blackens then does this suggest the bill has not turned and was black all along, thus pointing towards longipennis?

  • The legs looked really short both from a distance (when two longer-legged juvenile Common Terns were in the same view) and from closer.  This seems to be an indicator for longipennis.

  • In the field the grey underparts seemed to turn to white at around the lower breast, unlike photos of the Eastern Common Tern I had seen where it was grey up to the chin leaving just white cheeks.  But my photos, or at least some of them, do suggest the grey went further up, so maybe this isn't a problem after all?

  • The tone of grey on both upper and underparts is hard to assess.  In the field it seemed darker than typical Common Tern to me and to others with me, but I find it hard to be sure.  It would have been helpful if it had been among other adult Common Terns!  (It was on the first day I saw it, assuming I saw the same bird on each of three occasions, and did indeed look much darker).

  • On the first day I noticed the darkness extending on to the underwing, particularly along the trailing edge so leaving a paler centre of the wing.  I didn't realise it, but reading up since I find that's good for longipennis.

  • The forehead was clearly white - have those who have continued to see the bird at Cley (has anyone continued to see it?) noted its progress to winter plumage?  Is my bird consistent with how that bird (whether or not it's the same bird) now appears?  Similarly what about the smudge of dark extending on to the cheeks?

As this bird wasn't in full breeding plumage, the blackness of the bill isn't as clear an indicator of eastern origin as it might have been.  Maybe picking out longipennis with any degree of confidence is just too ambitious at this time of year? 

Plate 88 in the Helm guide to Terns of Europe and North America is interesting.  It shows a bird that's very similar to the one I saw, although with slightly less white on the forehead.  The caption states that it's unusual for a bird in such an early stage of moult to show a dark bill and concludes: "This and the very dark outer primaries may be characters of subadult."  If this speculation is correct then could the same be applied to my bird?  Or, given the grey plumage and short legs, could the bird in plate 88 even be longipennis?  Is that bird really within normal variation of hirundo?  If that is hirundo then I see no clear reason why my bird wasn't too.  What do you think?  Is it the wandering longipennis that I've been seeing, or just a normal western Common Tern?

Common Tern, Burnham Overy, 20th September 2014