Category: Warblers

After an absence of forty-seven days, the ‘eastern’ Lesser Whitethroat, which had made sporadic appearances in Dave Jackson’s Northampton garden back in January, returned today. Dave managed to capture some images which partly show the tail pattern – a largely white outer tail feather (some faint clouding at the distal end of the inner web) but it’s still not possible to see if there is any white at the tip of the adjacent feather, T5. Is it there or has it worn away (as the tail feathers appear quite abraded)? A video-grab of mine made back in January hinted at its presence but may be inconclusive. Either way, this bird pretty much ticks all the boxes for Central Asian Lesser Whitethroat, the name now being proposed here for birds in the group somewhere within the blythi—halimodendri spectrum.

The wintering Lesser Whitethroat made sporadic appearances in Dave Jackson’s garden again today, being seen only briefly once in the early morning, again at 11.50 and then again at 15.10, after which it appeared on three more short occasions with the last at about 15.50, which was just long enough for Dave to capture some more images and for me to snatch some video.

Eastern Lesser Whitethroat, Northampton 18th January 2014 (Dave Jackson)

Eastern Lesser Whitethroat, Northampton 18th January 2014 (Mike Alibone)

What a difference a day makes! The lighting was different today and the bird looked much, much browner – sandier even – than yesterday, adding weight to its likely eastern origin. Thinnish bill, very brown, almost ginger-toned, tertials and primary projection possibly on the short(ish) side. Still unable to get a view of the outer tail feathers to assess the extent of white. This bird could also appear quite long-tailed, a little pinched in toward the base, giving it almost spoon-like appearance at times.

After some research it’s now looking pretty good for halimodendri (Central Asian Lesser Whitethroat), a view forwarded by Gary Pullan, who also saw the bird today. Its pro-‘eastern’ features include brownish nape merging into grey of crown, sandy-brown upperparts, minimal dark mask, white throat contrasting with noticeably peachy-buff flanks and breast and apparently shortish wings, with the primary projection c.50% of the length of the tertials (nominate curruca said to be c.70%). But it could still be Siberian blythi …

Thanks once again to Dave Jackson for more images. I would welcome any comments or thoughts on the bird’s racial identification.

Dave Jackson forwarded these images he took of a Lesser Whitethroat in his Northampton garden today. A winter Lesser Whitethroat in the UK is exceptional and most – if not all – of these are likely to be birds of one of the eastern races.

I was struggling to stretch the ID beyond nominate curruca – it’s not particularly brown above (although the 4th image in the above sequence depicts more brown), the primary projection is not particularly short and you can’t see the extent of white in the outer tail feathers.

However, Martin Garner, who saw saw the images late this afternoon, suggests the smart money is on blythi – Siberian Lesser Whitethroat. If the bird is trapped, biometrics, DNA analysis and outertail feather pattern will all play a cumulative role in assigning the bird to race, while sound recordings and sonograms of the bird’s call (Sardinian Warbler-like rattle vs. standard ‘tac’ call of nominate Lesser Whitethroat) will also add weight. We’ll see.

Hume’s Warbler, Hume’s Yellow-browed Warbler, Hume’s Leaf Warbler – it’s the same whichever way you cut it. Once regarded as a race of Yellow-browed, it was split by the BOU in the late nineties and, with approximately 123 UK records, it’s a national rarity.

This one, seen fleetingly on private land on 6th December, was initially identified as a Yellow-browed Warbler and the identification remained as such until yesterday afternoon (7th December), when it was seen well and heard calling frequently. Identification was confirmed beyond the shadow of a doubt based on the diagnostic call, which differs markedly from Yellow-browed Warbler. For an example listen here.

Assuming this record is accepted by the British Birds Rarities Committee, this will be the first for Northamptonshire and only the second for an inland county following one at Westport Lake, Staffordshire on 20th December 1994 (although one in Essex in 2004 was also subsequently seen in Middlesex). However, it is not the first occurrence of this species in Northamptonshire. One discovered by Dave Jackson at Weston Mill, Northampton on 23rd-24th October 2010, remaining in deep sallow cover, was never seen well by local observers and its frequently uttered diagnostic call was impossible to sound record adequately against the background traffic noise from the nearby Nene Valley Way dual carriageway. As a result, the record found its way into the ‘not proven’ category of the British Birds Rarities Committee files.

Seeing it

At present there is no general access to the private Northamptonshire site. If the bird remains there is an intention to provide escorted access on Wednesday 11th December 2013. It is planned to accommodate three time slots of 9 am, 11 am and 1 pm for small numbers of birders only. Should anyone wish to attend please contact Neil McMahon neil.mcmahonoriole@btinternet.com who is arranging access and escorting observers on site. Anyone booking for the 9 am time slot is advised to be on-site in any event (the disadvantage of this early slot is that it may not be possible to confirm the presence of the bird by this time).

Please indicate which time slot is preferred. On confirming the appointment Neil will provide a rendezvous point and his mobile number.  Please be advised that there may be a delay in his being able to respond. Neil will visit the site early on Wednesday to establish if the bird is still present and update Birdguides and northantsbirds.com accordingly.  It is therefore advisable to monitor these websites on Wednesday for any relevant news.

Future access after Wednesday 11th December date may not be possible.

The sewage outfall stream from Ecton Sewage Farm into the River Nene near Cogenhoe has long been a regular magnet for Chiffchaffs during the winter months although it, along with the adjacent extensive Phragmites reedbed, receives surprisingly little attention from local birders. In winter the temperature of the treated water from the processing works is a few degrees higher than the surrounding environment and, as a result, provides a microclimate favourable to various insects and other invertebrates, which act as a ready source of food for insectivorous species like Chiffchaffs.

I visited the site in early January and was delighted to find at least three Bearded Tits and four or five Chiffchaffs in the general area. When Bob Bullock went there on 25th, however, the number of Chiffchaffs had increased to at least a dozen, all concentrated along the banks of the outfall stream, probably as a result of the recent cold snap. On 26th Bob visited the site again and found three ‘non-conformist’ Chiffchaffs among them – individuals which, on plumage, were clearly not of the nominate race collybita and which looked good for having an origin from much further east.

Armed with a phoneload of Chiffchaff songs and calls, plus a Bluetooth-enabled, thumb-sized remote speaker, I visited the site the following day, 27th, where I met up with Bob and together we eventually had prolonged views of two ‘grey’ individuals along the 150 metre length of stream immediately before its discharge into the river.

On plumage alone these two birds, almost identical in appearance and, differing markedly from the accompanying ten or so ‘regular’ Chiffchaffs, looked good for the Siberian race tristis based on identification criteria recently published here by Martin Garner.

Racial identification of Chiffchaffs has endured a chequered history in recent years. Initially it was thought to be relatively easy: if a grey-brown Chiffchaff sporting supercilia and secondary covert wing bars of varying degrees of prominence greater than a nominate race Chiffchaff called with a distinctive “peep” note, sounding like a ‘lost chick’, then it was tristis.

Then came the abietinus problem. This race, from Scandinavia/Western Russia, was believed to be greyer, prone to exhibiting wing bars, and was deemed a potential source of confusion with tristis. It was therefore believed that the only ‘good’ tristis were brown, buff or shades thereof. Then there was the tristis/abietinus hybrid zone with the potential to produce birds unassignable to race and which could wander to Britain …   With the publication of MG’s work on tristis identification it has come full circle. In it he outlines a study undertaken on trapped birds in The Netherlands. The bottom line result was that, in a small sample unit, all individuals identified as abietinus in the hand were actually tristis on subsequent DNA analysis! MG postulates that almost all abietinus probably migrate southeast in autumn and that this race is likely to be very rare in the UK. So tristis is back on the menu for British birders as being relatively straightforward to identify – especially if you hear the call.

Which brings me to an initial point of worry: neither of the Siberian Chiffchaffs was heard to call. I played recordings of calls and songs of all three races to them and, aside from one tristis and a couple of nominate collybita breaking cover just once to see what was going on when the regular Chiffchaff song was played, there was no reaction. None.

By good fortune MG was visiting the Bedfordshire Bird Club two days after the observation so, armed with numerous photos, Bob and I met up with him briefly to discuss the ID of the Ecton birds. Upon seeing Bob’s photos his view was we could confidently identify our birds as tristis – without even hearing the call! 

So, moving forward, firstly, we should be on the lookout for more of these birds, especially this winter as there seems to be more about nationally than usual and, secondly all the past records of abietinus in Northants can surely be removed as it appears they are not even readily identifiable in the hand – let alone in the field! These include individuals which have occurred at Ecton in past winters as well as others elsewhere.

For the record, there have been a handful of sight records of presumed Siberian Chiffchaffs in Northants and one of a bird trapped at Stanford Reservoir on 6th December 2008, which was confirmed as tristis by DNA analysis of feather samples. Field identification, though seemingly a lot clearer now, is still probably a ‘work in progress’.

I would like to thank Martin Garner for his input on the ID of the above birds and Bob Bullock for his excellent series of photographs.

* Nils Van Duivendijk Advanced Bird ID Guide – The Western Palearctic

Blackcaps are not an uncommon sight in Britain during the winter months nowadays. We have a ‘healthy’ wintering population of around 3,000 individuals which compares with a summer population estimate of 932,000 pairs (Birdlife International, 2004). Numbers wintering in the UK have increased considerably since the 1960s and it would seem likely that the above number is an old and conservative estimate so if anyone has an up-to-date figure I would be pleased to receive it.

Numbers wintering in Northants appear to have risen and averaged higher since the early 1990s, although this may reflect better observer coverage and communication.

Ringing data have established that UK winterers are from a breeding population in central Europe and, while most Blackcaps from this area head south-west in autumn to winter in Spain and northern Africa, some head north-west to the UK. The driver for this is not clear but milder winters and an abundance of ‘artificial’ food (i.e. winter bird feed provided by man) have been cited as the likely reasons. The latter of the two factors appears to be the subject of debate as many observations on wintering Blackcaps point to their feeding primarily on natural food sources such as berries and insect larvae when these are available.

Dave Warner’s excellent portrait of a male in his Northampton garden last weekend illustrates this point perfectly with the principal choice of food, Dave suggests, being an abundant supply of crab apples. That said, it seems logical to assume that ‘artificial’ food may at least act as a regular supplement or backup in the absence of natural foods, thus helping maintain the wintering population.

What is clear, however, is that our wintering Blackcaps are very different from those which breed here in summer. Having a shorter distance to fly to their breeding area in spring means they arrive back before the Spanish winterers and therefore only have each other to mate with, effectively becoming reproductively isolated from the Spanish birds.  So now there are morphological differences emerging. This population, in the space of little more than 50 years, has produced birds with rounder wings (as they don’t need to migrate so far) narrower and longer bills (supposedly for taking advantage of ‘artificial’ foods) and browner mantles and bills. A kind of ‘catalytic evolution.’ How far will it go? Full speciation?

So next time you come across a Blackcap in Britain in winter it’s worth remembering that it’s not just any Blackcap, it’s likely to be a breakaway Blackcap – an activist, a rebel, a pioneer and, although a potential champion of speciation, it may only ever become genetically distinct to a racial level, so don’t hold your breath for an ‘armchair tick’ any time soon …

For a more detailed look at this unfolding phenomenon see here and here.

A Firecrest is guaranteed to brighten the most dismal of days and the dank, drizzly conditions of Tuesday, 23rd October was one such miserable day in an extended period of late autumn gloom. Happily for Mick Townsend of the Stanford Ringing Group, this cracking little sprite found its way into one of the SRG’s nets from which Mick extracted it before ringing it and taking the below photographs yesterday morning. This is the only Firecrest to have been found in Northants this year. In a standard year there are, on average, 1-2 records (13 in the last 10 years) with the highest likelihood of a chance encounter with one in January or November.                                                                           The obviously spiky tips to the tail feathers suggest this is a first-year. Many thanks to Mick for his images.

This morning I spent some time at Stanford Reservoir with the Stanford Ringing Group. With summer all but over, the number of birds trapped was relatively low with 48 new birds of 13 species ringed (25% of which were Swallows) and 18 retraps of 11 species.

When not singing or calling, two of these species, Chiffchaff and Willow Warbler, present perennial ID difficulties for many birders in the field but not, of course, in the hand where biometrics and key features not obviously visible to field observers make separation easy. However, one of these features – namely wing structure – can be used in the field, if the bird stays still long enough for it to be assessed! Willow Warbler has longer wings than Chiffchaff, which is illustrated well in the below set of photos of two of the individuals trapped at Stanford this morning.

These two photos show the diagnostic emarginated 6th primary of Chiffchaff and its absence in Willow Warbler – not visible in the field, of course – but in the image of Chiffchaff the short first primary is tucked away and not visible and the second primary is barely visible behind P3.

The above two show the difference in length of primary projection: in the Chiffchaff it is little more than half the length of the visible tertials while Willow Warbler has a much longer primary projection – often the same length as the tertials and at least three quarters the length in the shortest instance (click on image to enlarge).

Now have a go and apply this to the bird below, recently photographed by Doug McFarlane in Moulton.  See here for the correct answer!
The final image is a bright juvenile Willow Warbler which, with its vivid yellow upper breast and whitish belly, is a pitfall for the unwary, sometimes accounting for erroneous reports of Wood Warblers in autumn …

Many thanks to John, Mick, Adam and Dawn for putting up with me and allowing me to photograph ‘their’ birds at Stanford this morning!

Nearly a month later, on 9th September, while ringing birds at St Andre, Portugal, John retrapped the very same Reed Warbler he had ringed at Stortons on 14th August. How amazing is that?! Same ringer, same bird, different country. What are the odds of this happening? I don’t know but I’ll be getting John to pick my lottery numbers from now on …

The Stanford Ringing Group has again been busy trapping rare warblers, having yesterday netted Northamptonshire’s second only Northern Willow Warbler. Identified on biometrics this race, acredula, which breeds as close as Norway, is regularly recorded on passage in the UK but what an odd time to find one inland in the Midlands!

Normally Willow Warblers start moving south at the end of July. So where did it originate? It is a female with a brood patch growing over so maybe from Scotland (where this race is believed by some to breed) or maybe a Scandinavian breeder whose brood has failed and it decided to return south early? I would be pleased to receive comments on its possible origin. Interestingly, the only previous record of this race for Northamptonshire was also trapped by the SRG on 23rd August 2008.