Northern Willow Warbler at Stanford

Northamptonshire’s fourth-ever Northern Willow Warbler was pulled from the nets of the Stanford Ringing Group, at Stanford Reservoir, this morning.

Willow Warbler comprises three subspecies – nominate trochilus from Britain, central Europe and southern Scandinavia, acredula (‘Northern Willow Warbler’) from northern Scandinavia, Russia and western Siberia and yakutensis (‘Siberian Willow Warbler’) from central and eastern Siberia. However, the subspecies are not well defined and there is extensive intergradation. Furthermore, variation is not linear, and birds showing the characters of one subspecies occur regularly within the range of another (BWP).

Northern Willow Warbler, Stanford Res, 21st August 2018 (Chris Hubbard)

Fortunately, visual characteristics, when combined with in-hand biometrics allow identification of acredula to be made. Trying to do so in the field, however, is more than a challenge on an out of range individual! This one is a typical, cold, pallid individual, with reduced yellow tones and quite a striking supercilium.

Northern Willow Warbler (left) and Willow Warbler, Stanford Res, 21st August 2018 (Chris Hubbard)

This is the fourth record of acredula for Northants, all of which to date have been trapped at Stanford! Previous records were 23rd August 2008, 30th June 2011 and 8th September 2014.

 

Marsh Warbler at Stanford

A routine ringing session at Stanford Reservoir this morning produced Northamptonshire’s fourth-ever Marsh Warbler.

It was trapped, ringed and released along the rear edge of Blower’s Lodge Bay at approximately 11.00. Thanks to Chris Hubbard for the images below.

Juvenile Marsh Warbler, Stanford Res, 9th August 2018 (Chris Hubbard)

The lack of contrasting rufous rump (of Reed Warbler) is an immediate pointer to identification, as are the pale-tipped primaries, although they are not as obvious as on some Marsh Warblers. Also pale fringes to tertials are more obvious than on Reed Warbler.

Juvenile Marsh Warbler, Stanford Res, 9th August 2018 (Chris Hubbard)
Reed Warbler (left) and Marsh Warbler, Stanford Res, 9th August 2018 (Chris Hubbard)

Marsh Warbler’s slightly shorter bill, plus eye-ring and supercilium equally distinct compared to Reed Warbler’s, are just about visible in the above image. Visually, though, they are still difficult to tell apart!

Marsh Warbler is just about hanging on as a rare breeding species in the UK, with perhaps only eight pairs restricted to sites on the east coast. Otherwise, it is a rare migrant.

Interestingly, two of the previous three records are from Stanford and include one trapped on 17th June 1984 and a singing male on 16th May 1989. The third was a singing male at Stanwick GP, twenty years ago, on 7th-9th June 1998.

Please note access to Stanford Reservoir is by permit only, issued by Severn Trent Water Authority.

Blackcap Central

With nearly two weeks of winter behind us and a blast of cold, Arctic air dramatically influencing our weather conditions, increasing numbers of Blackcaps have been reported in local gardens over the past days. Previously dubbed ‘Central European Blackcaps’, their origins are now under scrutiny.

That Blackcaps from a breeding area in central Europe have been migrating to winter in Britain over the last sixty years has been demonstrated by ringing recoveries and is not in dispute. Nor is the fact that this population, in this short period of time, has undergone a rapid microevolution, producing genetically distinct birds with a different set of physical characteristics (see Breakaway Blackcaps).

Male Blackcap, Byfield, 10th December 2017 (Gary Pullan)

However, in recent years a small number of recoveries indicates that some may originate much closer to home and, to complicate matters, there have been recent UK winter (November to February) recoveries of Blackcaps ringed in summer in Britain. This suggests that at least a few may have lost the migratory urge, having decided to become resident in the UK. The proportion of the summer population involved is unknown and more work needs to be done to determine if this is occurring with any regularity.

In a collaboration between Oxford University, the BTO, Exeter University and the Max Planck Institute for Evolutionary Biology, Germany to improve knowledge of migration and breeding origin, a number of wintering Blackcaps have been fitted with Geolocators. These will reveal where they have spent the summer when retrapped back at their wintering sites. To learn more about wintering behaviour, movements and use of British wintering sites, colour-ringing is also being undertaken in parallel with this study, allowing individuals to be identified by unique colour combinations. Colour-ringed Blackcaps should be reported to the BTO, via here.

Dusky Warbler at Stanford Reservoir

… or is it a Radde’s?

Before packing up this morning, the last bird pulled from the nets of the Stanford Ringing Group proved to be a Northamptonshire first but the subsequent circulation of the in-hand images generated a debate over its identity and a good deal of controversy as a result.

A break in today’s somewhat inclement weather provided a two-hour window of opportunity for Mick Townsend to get some ringing in at the usual site in, and around, the Blower’s Lodge Bay area at Stanford Reservoir. MT was just making the final round of checking the nets when he noticed a dull, brown passerine in the bottom pocket of the last net he came to. Upon approach, and with the bird facing away, Mick thought it was a late Reed Warbler but when he came to extract the bird it was immediately obvious that it was a dark phylloscopus warbler with a hugely prominent supercilium. He quickly identified it as a Dusky Warbler, took some biometrics and then set about putting the news out but – sod’s law – his phone’s battery was virtually dead and he just managed to get a text out to Chris Hubbard, a mile up the road, before it died.

Dusky Warbler, Stanford Res, 19th October 2017 (Chris Hubbard)

Chris arrived within 15 minutes and took the images reproduced here. Because the ringing station is on private land (and access to the reservoir is by permit only) it was decided to release the bird in the scrub in the car park by the inlet. Sadly, for Northants birders, this release area is the wrong side of the inlet, i.e. in Leicestershire!


The bird was duly released at 11.05 and flew to the nearest cover. It was next seen at 11.35, in hawthorns along the Leicestershire bank, about 100 metres from the car park but this was a brief observation after which it disappeared and was not seen subsequently, despite a search by good numbers of observers, who had gathered there since its release.

Dusky Warbler, Stanford Res, 19th October 2017 (Chris Hubbard)

The images circulated later in the day produced a mixed reaction, with some birders believing it was a Radde’s Warbler. I have to admit it does show some pro-Radde’s features and it had me wondering at the time.

Dusky Warbler, Stanford Res, 19th October 2017 (Chris Hubbard)

Had it been seen in the field and heard calling then there would have been no debate over its ID but a bird in the hand can be a different matter altogether and the two species can appear so similar that, in some instances, the only sure-fire method to confirm the ID is by measurement of the depth and the breadth of the bill – neither of which was recorded in this instance.

Dusky Warbler, Stanford Res, 19th October 2017 (Chris Hubbard)

Pro-Radde’s features exhibited by this individual are:

  • very long, strong, broad supercilium, extending along the full length of the ear coverts
  • very broad, almost blackish eyestripe, almost as deep as the eye, contrasting markedly with the supercilium and, in some images, appearing slightly darker than the mantle
  • ‘mean-looking’ appearance
  • pale spotted (not plain) ear coverts
  • cinnamon under tail coverts
  • large orange feet and, from what is visible, palish orangey legs

Pro-Dusky features are:

  • supercilium almost uniform in colour, whitish in front of eye in some images (Radde’s is buffish in front of eye, contrasting with paler behind)
  • Mantle is wholly brown – confirmed by MT (olive-tinged to strongly olive in Radde’s)
  • Edges to closed primaries are pale brown (not greenish-tinged like Radde’s)
  • Underparts sullied and dull, lacking the faint, sometimes ‘clean’ yellowish tinge of Radde’s
  • Bill shows dark upper mandible with extent of pale limited to cutting edge only (Radde’s usually shows more extensive pale areas); note the left side conforms to this but there is more extensive pale on the right side!

Having studied a number of photographs, Gary Pullan has today put forward what may yet prove to be a new identification feature for these two species, namely that the bill depth at its base is broader than the diameter of the eye on Radde’s Warbler but not on Dusky – and this fits the Stanford bird. GP went on to state that, having seen this bird briefly in the field, the bill appeared weak-looking and the bird did not look bull-necked like a Radde’s Warbler does.

Many – if not all – the pro-Radde’s features, above, can also be shown by Dusky Warbler. The logical ID conclusion is, then, that this is a Dusky Warbler. So, another amazing bird from the nets of Stanford. What will be next and … will we get to see it?

Of further interest, a number of feathers became dislodged when the bird was ringed. These will be sent off for DNA analysis … to be sure, to be sure …

Siberian Chiffchaffs

It’s still there! After Doug McFarlane had brief views, and managed a long range shot, of a greyish ‘Chiffchaff’ in the willows between the yacht club and the dam at Pitsford last Friday, I decided to have a look at the weekend – unfortunately to no avail.

Doug’s image, posted on Twitter the same day, did look pretty good for Siberian Chiffchaff, though. Fortunately, Bob Bullock rediscovered it in the same place only yesterday afternoon. This time it offered more prolonged views and allowed a closer approach, enabling some rather more detailed images to be taken. It still has yet to be heard calling, though …

Siberian Chiffchaff, Pitsford Res, 25th November 2015 (Bob Bullock)
Siberian Chiffchaff, Pitsford Res, 25th November 2015 (Bob Bullock)
Siberian Chiffchaff, Pitsford Res, 25th November 2015 (Bob Bullock)
Siberian Chiffchaff, Pitsford Res, 25th November 2015 (Bob Bullock)
Siberian Chiffchaff, Pitsford Res, 25th November 2015 (Bob Bullock)
Siberian Chiffchaff, Pitsford Res, 25th November 2015 (Bob Bullock)

One was also found by Gary Pullan in willows by the causeway at Ravensthorpe Reservoir on Tuesday (24th).  This race is still a rare visitor to Northants but it appears to be being seen with increasing frequency, with Ecton Sewage Farm a hot favourite for harbouring them among numerous Common Chiffchaffs in mid-winter. At this time the sewage farm outfall to the River Nene provides a slightly warmer micro-climate favourable to insects on which they feed. More about this, along with further images from Bob, here.

Blimey, it’s a blythi !

A Northamptonshire first

Confirmation came today that the ‘eastern’ Lesser Whitethroat trapped and ringed at Stanford Reservoir on 12th October was indeed of the race blythi – more commonly known as ‘Siberian’ Lesser Whitethroat. This is, therefore, the first confirmed record of this subspecies in Northamptonshire. Great news, broken this afternoon by Martin Collinson of the University of Aberdeen.

Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)
Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)

 

Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)
Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)
Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)
Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)
Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)4
Siberian Lesser Whitethroat Sylvia curruca blythi, Stanford Res, 12th October 2015 (Paul Riddle)

A big thank you is due to ‘Doc Martin’ who undertook the DNA analysis on a couple of feathers which became dislodged during processing. Martin, Chairman of both the BOU Records Committee and the British Birds Editorial Board, was also instrumental in confirming the ID of Britain’s first Acadian Flycatcher in Kent, earlier this autumn after, analysing its poo collected on site at Dungeness!

But where does this leave the 2014 ‘eastern’ Lesser Whitethroat which frequented Dave Jackson’s Northampton garden on and off throughout the winter? It will go down as ‘showing characteristics of’, of course, but the Stanford bird clearly demonstrates they can occur locally and it surely was one …

Probable Siberian Lesser Whitethroat, Northampton, 11th March 2014 (Dave Jackson)
Probable Siberian Lesser Whitethroat, Northampton, 11th March 2014 (Dave Jackson)

Stanford’s Eastern Dynamic Duo

We are in the midst of a Siberian invasion. The fallout from the arrivals en masse on the east coast – and elsewhere – has clearly penetrated far inland with the county’s second Yellow-browed Warbler of the year being trapped today at Stanford Reservoir. But that’s not all. Also pulled from the net was an ‘eastern’ Lesser Whitethroat – this hot on the heels of the presumed blythi individual which wintered in Northampton in 2014.

'Eastern' Lesser Whitethroat and Yellow-browed Warbler, Stanford Res, 12th October 2015 (Adam Homer)
‘Eastern’ Lesser Whitethroat and Yellow-browed Warbler, Stanford Res, 12th October 2015 (Adam Homer)

Adam Homer kindly provided some quick initial images (more to come) and an overview of the external features of the Lesser Whitethroat:

The biometrics pretty much matched up to the nominate race curruca so it looks likely to be blythi. We have ruled out halimodendri due to no white pattern on the 5th tail feather.
The bird was noticeably brown all over the mantle, rump and down to the tail.
The flanks were buff and belly was white. The head was brown with a slight greyish tone surrounding the black mask. Straight away whilst extracting it MickTownsend noticed that its eye was brown not unlike an adult Dunnock’s. Legs were slate-grey and soles of feet were cream. The upper mandible was blue-grey and lower was light grey at the base and blue-grey towards the tip.

Feathers which became detached during processing have been retained for DNA analysis, which Dr.  Martin Collinson (the legendary ‘Doc Martin’) at the University of Aberdeen has kindly agreed to undertake to help determine subspecific identity. Results are eagerly awaited !

Yellow-browed Warbler

The first of many?

Given the huge numbers of Yellow-browed Warblers present in Britain (more than 740, with 320 in Shetland alone) during the last week, it seems almost inevitable that at least one would find its way to Northants. And so it did. When Katie King was ringing at Kingswood, Corby yesterday she pulled this little sprite from the net.

Yellow-browed Warbler, Corby, 30th September 2015 (Andy Glover)
Yellow-browed Warbler, Corby, 30th September 2015 (Katie King)

Despite their apparently increasingly common autumn occurrence on the coast, they are by no means annual in the County with only six previous records (two in 1981, 1992, 2001, 2004 and 2010).

Let’s hope more are found locally over the coming weeks!

Central Asian Lesser Whitethroat: it’s back!

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.!cid_84C8967F-563F-4BB1-86AF-C1CE84A1EC60 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.!cid_0E5171D5-9804-4779-97F9-E5DF0446781E 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. !cid_734F3360-04E3-4280-B0E5-141AFD0AD623Either 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 blythihalimodendri spectrum.

More on the presumed ‘Eastern’ Lesser Whitethroat

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