Category Archives: d) Terns

Saunders’s and Little Terns ID pitfalls

 

Yoav Perlman

This is a topic I talked about briefly in my 2015 Spurn Migfest talk. Saunders’s Tern is one of the rarest and least-known breeding birds in the WP. Despite having a large range around the Indian Ocean, including Red Sea, coastal East Africa, Arabia and Indian Subcontinent, it is still a poorly-known species worldwide. ID of adults in summer is better described. Compared to its sister Sternula species, Little Tern, it is smaller and slimmer. Seeing them side by side (I have seen two in Israel alongside Little Terns), you get a similar comparison to Common versus Arctic Tern in differences in size, structure and derived flight pattern – about 10% smaller and more delicate, and flight more light and bouncy. Calls are also different – check the Xeno Canto page with lots of variation in call but the mainstream seems to be softer and less coarse than Little Tern. Some plumage features seem to be rather robust – first of all, contrary to what some birders may think, adult summer Saunders’s are paler above than adult little, very pale silvery-white. They have a larger dark primary patch, usually 4-5 dark primaries, compared to the normal 2-3 dark primaries in adult Littles. Also, Littles have a contrasting white rump and tail, at least the outer tail feathers (apprently greyer central tail feathers are quite normal in Little Terns). Saunders’s has concolorous (pale) grey mantle, rump and entire tail. And that’s it more or less. All the other features mentioned in literature are of unknown validity, mainly becuase the limits of variation within Saunders’s Tern, even adults in summer plumage, are little known.

But that’s not the only reason why separating these two species is challenging. Interestingly, the amount of variation shown by adult summer Little Tern, which is such a familiar and popular European bird, a photographer’s favourite, is not well described. More on this below.

My interest in them increased a few months ago. I noticed this Saunders’s-type tern in a blogpost of my good friend from Kuwait, Mike Pope from late April 2015:

Tern sp. with little Tern in background, Sea City, Kuwait, 25/4/15 by Mike Pope

Tern sp. with little Tern in background, Sea City, Kuwait, 25/4/15 by Mike Pope

This bird made some alarm bells go off – look at this broad wing patch (4 primaries), concolorous rump and complete grey tail – this must be a Saunders’s Tern, no? I flagged it up to Mike, he circulated among some experts, and the views were leaning towards Saunder’s tern – that would have been a long overdue first for Kuwait.

But then the plot thickened. I circulated Mike’s report among my fellow IRDC members. Yosef Kiat has been ringing Common and Little Terns for several years now in a breeding colony at Atlit, south of Haifa, on the Med Coast. He sent me some images of Little Terns from the breeding colony this late summer that knocked me off my chair. I was aware of the variation they show there, I did join him several times on his nocturnal adventures there, but have never seen extreme birds like these. First, a 2cy bird – this bird hatched in the colony to ‘normal’ looking Little Tern parents in 2014, and was retrapped this year:

2cy Little Tern, Atlit, israel, 25 August 2015 by Yosef Kiat

2cy Little Tern, Atlit, israel, 25 August 2015 by Yosef Kiat

Look at the grey rump and tail: perhaps outer tail feathers are slightly paler than the heavily abraded and dirty central tail feathers, but I am sure in the field this would look like a solid grey tail.

And take a look at this 1cy bird, hatched 2015, again to’normal’ Little Tern parents, wow!

1cy Little Tern, Atlit, 1/9/15 by Yosef Kiat

1cy Little Tern, Atlit, 1/9/15 by Yosef Kiat

Hmmm…. Grey rump, grey tail… And the wing looks like this – in the field it would look like a huge dark wedge:

1cy Little Tern, Atlit, Israel, 1/9/15 by Yosef Kiat

1cy Little Tern, Atlit, Israel, 1/9/15 by Yosef Kiat

Also this summer, in June, Yuda Siliki, an Israeli birder sent me this nice comparison of Little Terns from Ma’agan Michael – these birds are from the same colony in Atlit. Check out the variation in supposed features for Saunders’s Tern – shape of forehead patch and extent of dark bill tip. Saunders’s has much more limited white foreahead, not unlike the lower individual, but the white patch needs to more squared off in Saunders’s, less of a supercilium above and behind the eye, but still check the amount of variation among the two. Also, what about the amount of dark on the bill tip? Saunders’s should have more extensive dark than little, so what’s going on here?

Adult Little Terns, ma'agan Michael, Israel, 7/6/15 by Yuda Siliki

Adult Little Terns, ma’agan Michael, Israel, 7/6/15 by Yuda Siliki

I think it is very interesting to explore this species pair now. They were found breeding only recently in southwest Sinai, just 150 km away from the Mediterranean. For a long-distance migrant to hop into the Med is no big deal, and then it could practically turn up anywhere around the Mediterranean. An adult in summer plumage should be possible to pick out among Little Terns, but what about a young bird? and a non-breeding bird? Headache. If you read carefully Klaus Malling Olsen’s tern book he does state that in non-breeding and juvenile plumages it would not be safe to separate the species. With the circumstancial evidence provided here I tend to agree, but it is hard for me to accept that they cannot be separated. There must be something out there to teach us.

This is how some Saunders’s Tern breeding in Sinai look like – many thanks to Rich Bonser for allowing me to use his brilliant pics. Adults have a nice prominent wing patch, but only three dark primaries here. Is it moulting? Unclear. It has a small forehead patch, that doesn’t extend above and behind the eye:

Adult Saunders's Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

Adult Saunders’s Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

Difficult light conditions here. Rump is grey – however in this image tail looks paler?

Adult Saunders's Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

Adult Saunders’s Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

This bird in better light conditions does show the rump and tail pattern nicely. It is in active primary moult, so wing patch much reduced here:

Adult Saunders's Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

Adult Saunders’s Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

More extensive white forehead patch here, but again does not extend back above eye:

Adult Saunders's Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

Adult Saunders’s Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

Very pale silvery white above. Solid dark bill tip as in all photos. There is some talk about Saunder’s having duller leg colour but I think this feature is not worth much. This is so dependent on the hormonal condition the bird is in during breeding. Also bill tip must change according to breeding condition?

Adult Saunders's Tern, Ras Sudr, Siani, Egypt, July 2013 by Richard Bonser

Adult Saunders’s Tern, Ras Sudr, Siani, Egypt, July 2013 by Richard Bonser

This one below is a 1cy. I do not know if the colony at Ras Sudr is mixed with Little Terns or not, but in Rich’s blog this is a 1cy Saunders’s Tern – I will go with the flow. Not dissimilar to the Atlit 1cy Little Tern above? Pretty pallid bird but extensive wing patch. Greater and lesser primary coverts very dark here, but is it different to how the Atlit 1cy would look like in the field? I am not sure.

1cy Saunders's Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

1cy Saunders’s Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

1cy Saunders's Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

1cy Saunders’s Tern, Ras Sudr, Sinai, Egypt, July 2013 by Richard Bonser

It would be great to study the amount of variation the Sinai Saunders’s Terns show in key features like forehead patch, bill tip and tail pattern. Also how many dark primaries do they have before moult?

One incredible place to study Saunders’s Tern in non-breeding would be Kenya. I visited Sabaki river mouth, north of Malindi in December 2010. There is a roost of hundreds of thousands of Saunders’s Terns (!) there during the northern winter. I was there at daytime so there were only few thousands… But they were all distant, and scoping them into the sun didn’t provide me with much insight on their ID. I wonder if anyone rings them there, or at least photograhps them.

But one very important piece missing in the jigsaw is how much variation ‘our’ Little Terns show, in adult summer plumage and also in other plumages. Does this variation that I have shown here in Israeli birds occur in northern populations as well? The Little Terns I have seen here in the UK looked all bog standard, but I didn’t study any juveniles. I guess that few 2cy Little Terns return in summer to N Europe? Would be great to get some feedback from ringers and birders with field experience.

Sandwich Tern with yellow…

on more of the bill than usual

This curious looking tern was photographed on the 5th of November at Faro Saltpans in the south of Portugal. Thijs Valkenburg  is the guy who picked it up and in discussion with Pim Wolf came to a considered ID. I agree- see what you think. It’s interesting too when you recall that yellow-billed tern at Cemlyn, N. Wales a few years back. What have I said! 😉

Hi Martin,

 I got your email from Pim Wolf after discussing the identification of this tern. (see pictures attached)
 
We got to a fairly good conclusion we think, sandvicensis with a weird bill deformation and colouration.
 
We would like to see what´s your opinion about it. It´s quite a nice case. Lucky it was not a fly by,
that would be quite a heart breaking bird I think!
 
Best regards and thanks in advance for an answer,
Thijs Valkenburg

 

 

sandwich 1 sandwich 2 sandwich 3

 

Six of Eighteen

The Challenge Series: AUTUMN

One of the chapters covers Sandwich Tern and Cabot’s tern (the Sandwich Tern of North America). Twice young Cabot’s Terns have reached NW Europe as young birds in their first autumn, one in Britain and one in the Netherlands. Now that they have been recognised as full species- it’s about time another one appeared 🙂  For more on the content and how to buy the book click HERE.

Do you know which this one is?

One of them terns. Superb photo by a top photographer- if I tell you who took you'll know what it is.

One of them terns. Superb photo by a top photographer- if I tell you who took you’ll know what it is.

 

thumb

Antarctic Tern

Most Northerly Record Ever

by Chris Kehoe

With strange chequered markings in the tertials and  scapulars and worn blackish coverts, this young tern caused some initial head scratching. Many Antarctic Terns disperse northwards in the post breeding season and many young birds remain out at sea. This occurrence of a moulting juvenile Antarctic Tern found 7ookm further north than previous records suggests it’s not an entirely unlikely potential vagrant to the Western Palearctic, either via an Indian Ocean route or even perhaps via the Atlantic.

 

 

Madagascar (oct.-nov. 2013) 424b

This moulting juvenile tern was photographed on October 31st 2013 by Jean Neuray near Maroansetra in northeastern Madagascar during a Birdquest tour I was leading. When first seen briefly in flight, and against the light, a very pale trailing edge on the inner wing, glimpses of a neat dark trailing edge on the underside of white looking primaries and the overall structure created a strong impression of a young Arctic Tern – a vagrant to the tropical Indian Ocean with no previous records in Madagascar. However, when followed up and found settled near a few wintering Common Terns, Arctic was quickly ruled out. In particular the dramatic checkered pattern on the tertials is all wrong for Arctic Tern, the remaining juvenile mantle and scapulars are too dark and heavily patterned, the legs are a little too long and the plumage wear is more advanced than would be expected for a juvenile Arctic at such a date. Still, the bill proportions are similar to Arctic as is the head pattern with that big dark ‘panda’ eye patch, though it looked a little bulkier than Arctic around the head and chest. After a few moments the bird flew off with an elegant bouncy flight, viewed directly from behind but in better light than previously the secondaries were now seen to be very pale uniform grey, less white looking than on a juvenile Arctic, the rump and tail were mostly white though with greyer looking tail sides.

At the time I was perplexed by this combination of features, it was clearly not consistent with the appearance of any of the regularly occurring Malagasy tern species, though I vaguely recalled that the such a tertial pattern was a feature associated with Antarctic Tern and I tentatively suggested this possibility to my colleagues. As we were en route to the remote Masoala Peninsular to search for Helmet Vangas there was no immediate prospect of making further progress, all my relevant literature was at home and there would be no internet access, or even phone coverage for many days. When we eventually arrived in Antananarivo nearly a week later a quick Google image search seemed to confirm that Antarctic Tern was indeed the likely solution. Though no birds in exactly the same plumage state were depicted there were a few images of fresher plumaged juveniles showing a tertial pattern closely matching the Maroansetra bird.

juvenile Antarctic Tern, Sterna vittata vittata, 9 Aug 2009, Cape Columbine Nature Reserve, South Africa. Trevor Hardaker.

juvenile Antarctic Tern, Sterna vittata vittata, 9 Aug 2009, Cape Columbine Nature Reserve, South Africa. Trevor Hardaker.

juvenile Antarctic Tern, Sterna vittata vittata, 9 Aug 2009, Cape Columbine Nature Reserve, South Africa. Trevor Hardaker.

juvenile Antarctic Tern, Sterna vittata vittata, 9 Aug 2009, Cape Columbine Nature Reserve, South Africa. Trevor Hardaker.

Once back home it was possible to consult the literature (though rather little of use was found there) and to discuss the bird’s identity with others. The eventual consensus was that Antarctic Tern was indeed the best fit. Though few people knew the species well, and none were familiar with it in this particular plumage state, all were agreed that, realistically, it could not be any other species though it was necessary to extrapolate from images of birds in rather fresher plumage in order to secure a good match for Antarctic. One proviso though was that the immature plumages of the closely related and generally similar but very rare Kerguelen Tern seem to be virtually unknown, though young birds perhaps share the diagnostic grey tail of adults as do immatures of several other grey-tailed tern species.

Antarctic Tern breeds on various Subantarctic islands and on the Antarctic Peninsular during the austral summer but many disperse northwards soon after breeding. South Africa holds some quite large but very localised concentrations of post-breeding birds between April and October but the species then seems to lead a largely pelagic existence before returning to the breeding areas. Non-breeding birds also occur in southern New Zealand and along the coast of Argentina. Vagrants have been recorded in southeastern Brazil, in southern Australia and at Walvis Bay in Namibia.

The bird at Maroansetra therefore appears to represent the most northerly record ever, at 15.45°S it was approximately 800km further north than vagrants recorded in Brazil and Namibia (both at approximately the latitude of the Tropic of Capricorn) which are both about 700km north of areas of regular occurrence.

1cy Antarctic Tern Sterna vittata tristanensis. 26th Aug 2006 Mauritzbaai, South Africa. Trevor Hardaker

1cy Antarctic Tern Sterna vittata tristanensis. 26th Aug 2006 Mauritzbaai, South Africa. Trevor Hardaker

1cy Antarctic Tern Sterna vittata tristanensis. 26th Aug 2006 Mauritzbaai, South Africa. Trevor Hardaker

1cy Antarctic Tern Sterna vittata tristanensis. 26th Aug 2006 Mauritzbaai, South Africa. Trevor Hardaker

1cy Antarctic Tern Sterna vittata tristanensis 9th August 2009 Cape Columbine Nature Reserve, South Africa. Margaret Hardaker

1cy Antarctic Tern Sterna vittata tristanensis, 9th August 2009 Cape Columbine Nature Reserve, South Africa. Margaret Hardaker

1cy Antarctic Tern Sterna vittata tristanensis, 9th August 2009, Cape Columbine Nature Reserve, South Africa. Margaret Hardaker

1cy Antarctic Tern Sterna vittata tristanensis, 9th August 2009, Cape Columbine Nature Reserve, South Africa. Margaret Hardaker

How often Antarctic Terns reach so far north into the tropics is obviously unknown but there is surely a chance that some may be overlooked, especially once any distinctive juvenile features have been lost. In overall appearance Antarctic Tern is somewhat intermediate between Common and Arctic Tern though generally closer to the latter, both in plumage (seemingly including a simple wing moult strategy in adults) and structure. As some Antarctic Terns come into contact with wintering Common Terns in the Indian Ocean the possibilty must exist that an immature in particular could end up following flocks of that species as they return northwards. Arctic Tern is only a vagrant in the Indian Ocean north of South Africa with records in Somalia and Oman as well as in the Arabian Gulf and the Red Sea. However, anyone encountering a potential Arctic Tern in this region should be aware that Antarctic Tern also needs to be carefully considered. It may not be too outlandish to suggest that this highly pelagic species is also a potential vagrant to the Western Palearctic via an Atlantic route where both Common and Arctic Terns could act as carrier species, far stranger things have happened.

juvenile Antarctic Tern Sterna vittata vittata,18th May 2008, Mauritzbaai, South Africa. Trevor Hardaker

juvenile Antarctic Tern Sterna vittata vittata,18th May 2008, Mauritzbaai, South Africa. Trevor Hardaker

juvenile Antarctic Tern Sterna vittata vittata,18th May 2008, Mauritzbaai, South Africa. Trevor Hardaker

juvenile Antarctic Tern Sterna vittata vittata,18th May 2008, Mauritzbaai, South Africa. Trevor Hardaker

Thanks to Pete Morris, Klaus Malling Olsen, and Trevor Hardaker for useful discussions and comments and to Jean Neuray for capturing such a sharp image of the Maroansetra bird from a moving boat. Also special thank to Trevor and Margaret Hardaker for use here of their wonderful images.

juv and adult Antarctic Tern Sterna vittata georgiae, 15th Jan 2010 Grytvikren, South Georgia. Trevor Hardaker

juv and adult Antarctic Tern Sterna vittata georgiae, 15th Jan 2010 Grytvikren, South Georgia. Trevor Hardaker

Eurasian Sandwich Tern in North America

Amazing Ringing Confirmation

This post is informed by several discussions with Greg Neise about this European Sandwich Tern in Chicago in 2010, arguabley a North American first, and ‘poaches’ (following discussion!) from an eBird post here with Marshall Iliff and a BTO post by Mark Grantham

by Marshall Iliff, Mark Grantham and Martin G.

20130821_102746

Although Sandwich Tern is a primarily southern species in North America, the European subspecies is common north through the British Isles. The nominate form, widespread in the Old World from Europe to South Africa and east to India, was recently split from the two New World subspecies by the British Ornithologists’ Union (Sangster et al. 2011) based on a genetic study by Efe et al. (2009). Cabot’s Tern includes two subspecies: northern T. s. acuflavidus has the typical black bill with a yellow tip (just like Eurasian Sandwich Tern) while the more southerly T. s. eurygnathus–also known as Cayenne Tern–has a yellow or orange bill. Cabot’s Tern (subspecies T. s. acuflavidus) has occurred in the United Kingdom twice (records discussed by Garner et al. 2007). The North American Classification Committee considered a split in Sandwich Tern this past year but elected to await more compelling evidence. Despite this decision, it still seems likely that New World and Old World Sandwich Terns will eventually be universally adopted as a split. On 31 July, a long, thin-billed Sandwich Tern was seen on Cape Cod, Massachusetts at South Beach (see photo-illustrated checklist by Blair Nikula). Also of interest, the bird sported a metal band on its right leg. An unbanded Sandwich Tern was spotted at nearby Coast Guard Beach/Nauset Marsh–about 10 miles north–on 3 Aug (illustrated checklist by Ben LaGasse). On 18 August, the banded Sandwich Tern was seen again, this time at Nauset Marsh. It now had a much whiter crown but otherwise appeared similar, with a very long drooping bill; it was accompanied by a bird (also seen 15 August) that looked similar in size and structure but with a more extensive dark cap (illustrated checklist by Keenan Yakola). Finally, on 21 August, Jeff Spendelow of the U.S. Geological Survey was able to read the band number on the banded Sandwich Tern: the band read “British Trust, London”. 20130821_102714

Mark Grantham (BTO) takes up the story:

For such an important record we were eventually able to confirm the ring number with the finder and this was indeed a bird from Northumberland: DB67406 had been ringed as a chick on Coquet Island in 2002. With just one previous record of a ‘possible’ in Chicago in 2010 (details here), this bird could well turn out to be the first Sandwich Tern record for the USA.

DB67406 was seen by biologist Jeff Spendelow, who studies the use of staging sites by Roseate Terns in the Cape Cod area of southeast Massachusetts. It was first seen on one of his study sites on 31st July, but it wasn’t until 21st August that Jeff was able to read its ring, with it also later seen at nearby Chatham on 7th September (in red on the map below). Several other intrepid American birders managed to paddle out to the islands to see the bird, but it was hardly ‘twitchable’! Photographs of the bird do also show many of the features used to separate Sandwich from Cabot’s Tern, but you can’t argue with a bird ringed as a chick in Europe!

Interestingly, there is an equally unusual record the other way round, with a Cabot’s Tern from the USA being found dead in the UK (in green on the map below). NAW 110386842 was ringed as a chick at Beaufort, in 1984 and was found dead in November 1984 at the rather bizarre location of Newhouse Wood in Herefordshire. It was reported independently (as a tern/gull) by two observers so is genuine, and is the first record of Cabot’s Tern in Europe. There have since been further records in Europe (including a possible Cayenne Tern in Wales), but this remains a most bizarre first.

View Map of ringing recoveries: Sandwich and Cabot’s Terns 

Recent work at several Sandwich Tern colonies in the UK has seen large numbers of chicks being colour-ringed, an even better way of keeping track of their movements. At Coquet, 52 chicks were colour-ringed this year alone, with a further 102 on the Farne Islands. Of the latter, 11 have been seen further north in the autumn, from Musselburgh to Findhorn. Birds have also been colour-ringed in Norfolk, Grampian and The Netherlands, so plenty to keep an eye out for. Eurasian Sandwich and Cabot’s Terns are extremely similar. Garner et al. (2007) point out striking differences in juvenile plumage, with Eurasian birds having strong black chevrons on the scapulars in comparison to much more muted upperparts of juvenile Cabot’s Terns. In adult plumage they are much trickier to identify. Potential field marks include: 1) long, thinner, more drooping bill with less of a gonydeal angle in Eurasian Sandwich; 2) broader white fringe to the fresh primaries in Eurasian Sandwich; 3) typically earlier primary molt in Eurasian Sandwich; 4) more ‘salt and pepper’ speckling on the crown of Eurasian Sandwich, with the speckling extending farther foreword on the crown. The Massachusetts bird has a very white forehead and central crown, more like Cabot’s. However, the very fine speckling towards the rear crown may suggest Eurasian Sandwich. The freshly molted inner primaries visible on the 31 July photos by Blair Nikula could be a point in favor of Eurasian Sandwich and the pale tip, although hard to discern, does seem quite broad on the freshest primary. But overall, identification from plumage and structure may not be diagnostic; whether this individual can be confirmed as North America’s first Eurasian Sandwich Tern may depend on what is learned from the band details. There is just one prior suggestion that Eurasian Sandwich Tern has occurred in North America. Greg Neise, in a blog post discussing Illinois’s second record in September 2010, pointed out the very long, drooping bill of that bird and the molt pattern of the crown, making a case for North America’s first Eurasian Sandwich Tern. Chicago is so far outside the normal range of Cabot’s Tern, that either taxon might be almost equally likely here, so this was an interesting suggestion. Whether or not the ID of the Chicago or Massachusetts birds can be confirmed from the existing photos remains to be seen, but we strongly encourage observers to be aware of the possibility of Eurasian Sandwich Tern in North America and to extensively document any suspected occurrences. Within eBird, carefully identified terns can be entered as Sandwich Tern (Cabot’s), Sandwich Tern (Eurasian), and for the yellow or orange-billed population in the Caribbean, Sandwich Tern (Cayenne). Under all circumstances, we recommend identification at the subspecies level to be based on careful assessment of field characters, rather than assumptions about what subspecies seems more likely. As evidenced by this story, we still have much to learn and a significant proportion of the Sandwich Terns in the Northeastern U.S. and Atlantic Canada may in fact turn out to be trans-Atlantic strays rather than wanderers from further south on the Atlantic coast.

Comments on ID issues from Martin G.

Hi Mark
 
I have picked up the story and found other photos….
 
This is of course an amazing record whichever taxa is involved. Given that acuflavida has reached Europe and that there are instances of Nearctic species reaching Britain and returning to North America (Ring-billed Gull and maybe American Wigeon? spring to mind), I tried not to be swayed and see what identification features I could see on this bird irrespective of any known ‘life history’.
 
First point is that when we did the research which culminated in the Dutch Birding paper, we reckoned that the period in which the photos of this bird are taken (July and August in N America) is the most difficult to separate Sandwich and Cabot’s terns “with the effects of wear and moult at their peak during late summer and autumn, this may be the most difficult period to establish a frim identification”. Broadly speaking I still think this is true.
 
However there are some clues on this bird, at least as I interpret the photos (Blair Nikula’s are especially helpful).
 
1) The head pattern shows quite extensive plain looking white patch on the forehead to mid crown. 9410293319_124e53da19_oThe black rear crown feathers are relatively short and fairly obviously peppered with white tips etc. While the plain white area may suggest acuflavida I think it is OK for some sandvicensis. Sort of equivocal for adults. You would expect more black peppering in white area in 1cy birds. However the black rear crown feathers is for me more typical of sandvicensis than acuflavida. Short and obviously white peppered- versus in the vast majority of cases longer, greasy looking and any white tips very tiny on acuflavida- probably hardly visible on the quality of these images. While it’s not absolute and there may be extreme examples of both taxa that fit this head pattern, by gut would be it favours sandvicensis
 
2) The bill shape is quite deep based but I get the impression of a longish bill, obviously decurved slightly and rather fine over the distal half. Difficult to quantify and I wouldn’t stake the full ID (extremes of both taxa can be more obvious)  on it but on balance I would favour sandvicensis
 
3) Most compelling for me are the tips off the outer primaries. These feathers are all old and worn and the critical width of white on the inner web and feather tip is not longer visible. However in some birds white pigmented parts or feathers wear faster than black ones. This is perhaps more familiar in Two-barred Crossbills, in which worn tertials have no white tips left but the shape of the worn tertials can clearly be traced where the white pattern once was. On this bird in a couple of different photos you can clearly see the feather tip is not neatly rounded or pointed but has little ‘pimple’ for a tip- the inner web stopping short of the tip and leaving extra section of outer web extending on. This is the expected shape of wear for a sandvicensis with its broad white tip and broader white fringed on the inner web. On acuflavida the white fringes and tip is too thin to leave such an obvious wear pattern. You may well know that Greg Neise first flagged this up to me on the (to me obvious sandvicensis) he had in Chicago.
 
In short I think this is a ‘sandvicensis’. I am not sure I would be unequivocal/ 100% as I think that e.g. the Chicago bird is a more obvious example, however re-introducing the ‘ring’ element on this bird, the most parsimonious explanation is this is European Sandwich Tern, ringed in UK and travelling to N. American- based on both plumage/structure and parsimony.
 
For me it breaks through the credibility barrier- European Sandwich Terns can and do reach North American (as well s vice versa!)
 
Hope that helps
 
Cheers Martin

REFERENCES: 

Efe, M.A., Tavares, E.S., Baker, A.J. & Bonatto, S.L. 2009. Multigene phylogeny and DNA barcoding indicate that the Sandwich Tern complex (Thalasseus sandvicensis, Laridae, Sternini) comprises two species. Mol. Phylogenet. Evol. 52: 263–267.

Garner, M., Lewington, I. & Crook, J. 2007. Identification of American Sandwich Tern. Dutch Birding 29: 273–287. [online here]

George Sangster, Martin Collinson, Pierre-Andre Crochet, Alan G. Knox, David T. Parkin, Lars Svensson, Stephen C. Votier. 2011. Taxonomic recommendations for British birds – seventh report. Ibis 153: 883-892. [online here].

Eastern Common Tern – did one frequent Minsmere in 2011?

Eastern Common Tern – did one frequent Minsmere in 2011?

By David H Hatton, Royston, Herts, UK

In the late spring of 2011, I took a holiday based at Westleton, Suffolk, for a week together with fellow birding friend Tim Wilson and our families. Most days we would venture the short distance to Minsmere RSPB reserve for some birding and photography. During the course of these visits, we had encounters with many terns, but one in particular may be exceptionally interesting.

On the 30 May at 8.50 am Tim spotted an adult dark-billed tern resting some 40 metres from the south hide. Presuming it was going to be one of the few Roseate Terns present we switched to our scopes only for it to immediately fly off over the scrape and disappear seawards. In flight, the jizz looked wrong, lacking the long tail expected of that species. And, as Tim pointed out, shouldn’t it have had bright red legs?! – as his first brief binocular view had indicated the bird possessed dark legs, we scratched out heads and mused over whether a 1st or 2nd summer ‘portlandica’ Common Tern might be the explanation.

Later that week, on the 3rd June at 8.10 am, I was alone in the east hide at the end of a pre-breakfast walk down from Dunwich cliffs. Scanning the scrape, a tern suddenly grabbed my attention, sitting on one of the perching poles conveniently located to the left of the hide. Again I fell for the same trick – with my eyes briefly feasting on the black crown and bill, ‘great, Roseate’ I thought to myself as I instinctively switched to my digiscoping set-up and spent a few seconds slotting the gear over the eyepiece. The very moment the target snapped into focus, and before I could press the shutter button – it took off and started flying towards me. This time, I reached for my SLR and, with some relief, it locked on, allowing a couple of shots to be acquired (Figs 1, 2). Seconds later, the bird had passed the end of the hide and disappeared over the dunes towards the sea.

Again I was to be initially disappointed – its dusky not pinkish underparts, modest tail, rather ‘common’-like underwing pattern, with pale semi-translucent inner primaries contrasting with dark-tipped outer primaries and slightly darker grey secondaries, all suggesting Common Tern, Sterna hirundo. However, really bamboozling me was its quite un-‘common’-like bill – modest in length, delicate in structure and entirely blackish along its length save a hint of maroon at the very base of the lower mandible. Its completely black cap and neat body plumage suggested it was in adult summer plumage, but why that funny bill?

With some photographic evidence acquired and the end of the family holiday approaching, I resolved to follow it up later. I was likely to be stymied I thought by the brevity of my encounter and lack of detailed field notes, but, within days of my return, and with excellent timing, I noticed Sean Nixon’s account and photos that had just been published in Birding World (issue 293), of a presumed ‘Eastern Common Tern’, S. h. longipennis, at, where else but, Minsmere on 14 May 2011, putatively only the second record for Britain of this form. Until that point, I had forgotten about the existence of these birds that, unlike European birds, are black-billed in summer. That article, with its insightful additional editorial analysis, together with an update six months later (issue 300), arguing that a second bird was present at Pakefield (& possibly Alton Water), Suffolk 14 July 2011 and another, perhaps third bird, present at Heist, Belgium on 22 June 2011, convinced me that I should seriously consider whether I had fortuitously added a piece to the jig-saw of Suffolk ‘Eastern CT’ occurrences in 2011.

Below I tabulate the known features of Eastern Common Tern (believed to be useful for separation w.r.t. Common Tern) and compare them with the set of features of the ‘East hide’ bird. This summarizes information I have found published in Birding World issues 293, 300 & 303, Terns of Europe & North America (Olsen & Larsson, 1995) and the Advanced Bird ID Guide (N.v. Duivendijk, 2010).

Eastern Common Tern features in comparison with those of Common Tern (adults) Minsmere ‘East hide’ bird, 3 June 2011Similar feature present?
Slightly more svelte appearance YES, the bird was more elegant & less ‘stocky’ to my eyes, born out by the side-view photo
Smaller more domed head/crown YES, head neatly domed, less angular than CT
Slightly longer wings, outer tail feathers project slightly beyond wing-tips Not determined
Bill shorter & finer, sharper, less dagger-shaped (though some variability) YES, bill less ‘dagger’ proportioned appearing fine in side view
Bill black, some with crimson-purple at base of lower, brightening in spring YES, blackish, with small area of blackish crimson at base of lower mandible
Bill has less arched culmen YES, bill has quite delicate profile
Black crown has more sharply defined edges, sharper contours behind head YES, sharply demarcated edges to whole crown
Dark trailing edge to secondaries on underwing YES, grey distal secondary band contrasting with white greater coverts
Upperparts more ash grey Not determined, but perhaps hinted at by darkness of the underside secondary band
White cheek stripe, esp. in front of eye YES, contrasting moderately with pale grey upper breast
Underparts dusted with lavender grey, isolating a white cheek stripe YES breast & belly looked darker and more contrasty than other CTs seen in same light
Legs dark reddish brown/brown/chestnut Legs retracted & invisible in flight, not noted either way when briefly perched
Call less shrill Not determined (silent)

I conclude that the East hide bird of 3 June 2011 shares many of the features associated with Eastern Common Tern, especially the overall jizz and bill colour and structure, although the character set is incomplete because views of the upperparts and leg color were not obtained. No strong contra-indicatory features were noted. Could a ‘western’ Common Tern in summer ever show such a suite of features one wonders? The photos I obtained are not inconsistent with those published in plates 1–3 and 10 of Birding World issue 293 (pp. 211, 214) – if it is an Eastern type, perhaps the bird that Sean Nixon found was more than a one-off visitor to Minsmere in spring of 2011 – maybe it will return!

Acknowledgements

I thank Tim J. Wilson and Charles Fentiman for discussions during preparation of this note.


www.art16.co.uk

20 Apr 2012

Footnote –  See similarity from BirdQuest in Japan:

http://www.birdquest-tours.com/gallery.cfm?TourTitle=&start=3206