Crawford 08/03/2019: more Goldfinches and some dodgy looking Blackbirds

The weather has been pretty poor for mist-netting recently and the forecast looks even worse for next week so I decided to make the most of a brief weather window on Friday morning. A weak ridge of high pressure provided near perfect mist netting conditions for a few hours and, luckily, I was able to rearrange other commitments to take advantage of it.

The ringing site is baited every two or three days with the aim of ensuring food is never allowed to run out or run too low and ringing visits are generally limited to once per week or less, depending on the weather. As a general rule I would rather skip a week or two when it comes to ringing visits than try mist-netting in suboptimal conditions. That approach paid off again on Friday morning as the 3 hour session with one 18m net resulted in a catch of 48 new birds and 11 retraps.

Goldfinches topped the totals yet again, although that is not surprising given the success the species is currently enjoying and the high proportion of nyger and sunflower hearts in the seed on offer, but on the other hand Yellowhammers have been absent full stop and Greenfinches had been absent prior to this visit. The 2 Greenfinches caught in this session were the only ones recorded which is a very poor showing given the site has been baited for well over a month now. Greenfinch populations have seen a massive decline nationally large due to disease (trichomonosis) and there doesn't appear to be any prospect of that situation improving any time soon, if anything their decline appears to be continuing.

I don't catch many Reed Buntings at the site (only 11 individuals over the past 5 years) so it was good to catch one and more so because it was a retrap. Interestingly this male Reed Bunting was originally ringed 3km away on Billinge Hill in September 2015 and was previously retrapped at Crawford in March 2016. Most of the other retraps were from recent visits but all 3 retrap Blue Tits were much older with one having been ringed as a juvenile in June 2014 and the other two were ringed as first-years in December 2015.

Retrap male Reed Bunting

The second Blackbird caught during the session was interesting in that it had an unusual plumage. It was a brownish individual but the orange-yellow bill was strongly suggestive of it being a male. Some first year male Blackbirds can have a female like plumage and these birds are often termed 'Stockamsel' types which I have blogged about before (link here). However, it also had some feathers with what could be termed a frosted or white appearance. These frosty looking feathers were asymmetrical in that more were present left wing than the right. The tail was also affected but there was a bit more symmetry in the appearance of the tail. 

The appearance of the head and neck was not dissimilar to an old adult (2CY+) female as female Blackbirds occasionally acquire a near full yellow or orange-yellow bill with age.

The right wing was more female like than male with some slight frosting to the inner secondaries. There were 3 old greater coverts which points to it being a first-year bird and  is part of my reasoning for thinking it is more likely to be a male as the bill is far too orange-yellow for it to be a first-year female.

The frosty effect was much more extensive on the left wing but it still looks brownish overall and generally a bit more like a female than a male. There is one old greater covert which is shorter and just visible by the 2 heavily frosted greater coverts so points to it being a first-year bird like the right wing. The asymmetry wasn't just in the frosting as there were 3 old greater coverts on the right wing and there was only 1 on the left.

The tail was interesting in that the shape of the feathers was not dissimilar to those of an adult by being quite square ended but there are some obvious fault bars and other structural issues. The right central tail feather was a bit more pointed than the left but in all other respects (colour and wear) they were the same so it didn't look like one had been replaced. The frosting affected the the end portions of the 3rd, 4th and 5th feathers on the right and 2nd,3rd and 4th on the left. The outermost (6th) tail feather on the left was being replaced but you can see from the part that has emerged from the sheath that it is a similar colour to the main part of the other tail feathers and isn't coming through jet black like a male. It suggests this bird's appearance will remain similar to how it is now with any difference being more to do with the freshness of the feathers as can be seen in the upper-tail coverts with the newer longest upper-tail covert being a darker blackish-brown compared to the old worn brown upper-tail coverts. So this bird may not get any or much blacker as it gets older

The term 'Stockamsel' is attributed to the naturalist Johann Andreas Naumann and was first used a couple of centuries ago and has been used in the literature occasionally since then for those first-year male Blackbirds that have a more female like plumage. There is also the possibility that some of these 'Stockamsel' type birds are actually intersex as they display a mixture of male and female characteristics. That doesn't appear to have been considered before and I don't know that it has ever been ruled out. I found an interesting blog post which touches on this subject relating to wildfowl and possible confusion between hybrids and intersex birds which is worth a read (link here). I am no expert so I will stick with calling these dodgy looking Blackbirds 'Stockamsel' types until some research is done that confirms their sex and establishes the cause or causes for their appearance.

Now one 'Stockamsel' type Blackbird in a ringing session is interesting but I ended up catching another two which is exceptional in my experience.The other two didn't have the white frosting but in other respects were similar. In my previous blog post on the subject I refer to two I caught in the garden just over a week apart and I commented that if such birds weren't supposed to be of continental origin you would have thought they came out of the same nest. Now I have caught 3 on the same day and at the same site I do think local origin and same parentage could be a real possibility. Perhaps 'Stockamsel' types can originate anywhere in the species range if both parents possess a particular gene. There was nothing about the wing lengths of the three birds to suggest they were of continental origin in fact 2 of the 3 had relatively short wing lengths which, if anything, suggests they were more likely to be of British origin but then the fact that they have aberrant plumages probably means we shouldn't try and read anything into their wing lengths. Catching 3 on the same day certainly seems to make the chances of any of them being intersex a bit less likely but it can't be ruled out entirely.

Stockamsel type number 2 appeared to have 4 old greater coverts although the 3 outer were paler and shorter than the 4th but the outer 4 were browner than the blacker and newer looking next 3 inner greater coverts. Aberrant plumages can make ageing feathers more difficult for a variety of reasons not least because feathers of different colour can wear differently and birds with plumage aberrations may not always moult in the normal way, we simply don't know or can't be 100% sure. The 3 black greater coverts help make this one look more like a male.

Overall the 2nd bird was a bit blacker than the first individual but it is certainly not your typical first year male Blackbird

As with the first bird it is the near full orange-yellow bill that draws the eye and makes it look more like a male. Forget the bill and the plumage is intermediate.

I didn't photograph the 3rd Stockamsel type as it was very similar to the 2nd plus I had quite a few other birds to deal with at the time. The main difference was that it only had one old greater covert plus it was slightly longer winged (the wing lengths of the three birds were 126mm, 129mm and 132mm if you were wondering). Bottom line I caught 3 Stockamsel types out a total of 6 Blackbirds trapped in one session which, as I said before, is exceptional in my experience.

I am sure there could be a PhD for some upcoming ornithologist or geneticist if they do some research into this phenomena. Are they all males with some female characteristics or females with some male characteristics or something in between? Is there more than one cause?  Do they originate more frequently in some parts of the species range than others? Is it purely a first-year phenomena and do they always conform to type with the first full moult or is it the fact that Stockamsel types are relatively rare that makes finding a Stockamsel type adult that much rarer? If anyone out there has more information or has answers to any of these questions then please get in touch as I would be interested to know.

Ringing totals (retraps in brackets) for 08/03/2019 were: Collared Dove 1; Coal Tit 1; Blue Tit (3); Great Tit 2; Long-tailed Tit (2); Blackbird 5 (1); House Sparrow 2; Tree Sparrow 5 (1); Dunnock 1 (1); Chaffinch 1; Greenfinch 2; Goldfinch 28 (2); Reed Bunting (1). A total of 48 new birds and 11 retraps.

Siskins in short supply.

Things had been looking quite promising for Siskins in the garden this spring with birds starting to visit the feeders back in late December and then more regularly through January and into early February. Up to five were seen visiting the feeders in late December and that increased to between five and ten through January and into early February but then numbers fell away. That sudden and unexpected drop off in numbers was also mirrored by Goldfinches and other species so it wasn't just a Siskin thing which makes it a bit harder to understand.

The prospects for the spring looked to be good at the end of January with up to 10 Siskins visiting the feeders.

This is one of 7 feeders in the garden. All were well used in late January and needed topping up or filling every day.

The drop off in numbers of all species started ahead of the spell of exceptionally warm weather that came in late February but that doesn't mean the weather wasn't a factor. Temperatures could be involved as it has been quite a mild winter overall but wet or dry conditions can make a difference too. Cones on alder and conifers open and close in response to moisture levels which can make their seeds more or less easily accessible and their productivity also varies from year to year. The mild conditions have caused some tree buds to develop early and willow catkins to emerge which are another energy rich food source for Siskins and other finches. The fact that Siskins are variable migrants in terms of numbers and distances involved and can be very early breeders all adds to the complexity but it is all food related in one way or another. Bottom line it is currently looking like being a relatively poor spring for Siskins in my garden this year. Currently a maximum of three are visiting the feeders at any one time and then only on a fairly intermittent basis. If it was going to be a good spring for Siskins I would expect counts to be in double figures by now (18 were ringed in the garden on 6th March last year) with birds being seen in the garden throughout much of the day.

Ringing revealed there were a few more Siskins visiting the feeders than the counts alone had indicated, as is often the case, but the overall picture was the same. At least 7 different individuals visited the feeders in late December and one of those was a retrap that was originally ringed in February 2018. In January and February a total of 16 different individuals were captured: of these 12 were new birds, 3 were retraps that had been ringed in December and another retrap had been ringed in December 2017. In the past Siskins were exclusively late winter and spring visitors to the feeders but the last few years have seen small numbers arriving much earlier in the winter with some being ringed returning birds. It will be interesting to see if this trend of early arrival and winter to winter retraps continues or even increases in the coming years.

Male Siskin 31/01/2019.
I took a series of photographs of this bird and managed to read part of the ring number which pointed to it being one of the returning wintering birds.

Female Siskin 31/01/2019

There is still time for numbers to increase as we move further into spring but any build up in numbers will be much later than usual and is likely to involve fewer birds than last year, if it happens at all.  

Crawford: 24/02/2019

Fog delayed the start of the session and strong sunshine brought it to a close but in the two and a half hours the tall hedgerow provided shade for the 18m net a decent total of 41 new birds and 5 retraps were caught. The catch was dominated by Goldfinches but a few more Tree Sparrows appear to have found the seed and 9 were caught along with a couple of House Sparrows. There was no sign of farmland species like Yellowhammer but they may still be finding enough food in the surrounding fields. It appears to be a similar story with Corn Bunting with birds thinly scattered across the adjacent farmland and some appearing to be back on territory.

Tree Sparrows have increased in this area in recent years but their distribution is patchy and they are still absent from some of their former haunts.

House Sparrows don't seem to be doing very well anywhere and while the steep decline in their numbers may have levelled off to some extent there doesn't seem to be any indication their numbers are likely to recover anytime soon. 

The current spell of unseasonably warm weather is clearly having an effect with a Linnet back on territory and singing at the ringing site; Chaffinch, Goldcrest and Song Thrush were also in full song. Spring was in the air for Dunnocks too with a lot of singing, wing flicking and chasing going on while a pair of Long-tailed Tits was prospecting for a nest site in the brambles. A reminder that we are still in winter came in the form of a male Chaffinch and a male Blackbird that were caught and found to have long wing lengths. Both of these birds were likely to be winter visitors from the continent with the colour of the underparts of the Chaffinch also pointing to a continental origin.

Ringing totals for 24/02/2019 were: Blue Tit 6 (4); Great Tit 2 (1); Blackbird 2; House Sparrow 2; Tree Sparrow 9; Dunnock 1; Chaffinch 2; Goldfinch 17.

First outing in a while.

I obviously I haven't posted anything on the blog for a couple of months and that has been due to a number of factors, not least two more deaths in the family, but I have been keeping my hand in by doing a bit of ringing in the garden and keeping a look out for ringed gulls on Orrell Water Park.

However, I started baiting the farmland ringing site a Crawford a couple of weeks ago and decided to make my first ringing visit this morning. I knew there were plenty of birds coming to the feeders from the numbers I had seen on my last visit to top them up and by the rate the seed was being eaten so I only set up one 18m net.

The catching rate was brisk, as can be the case when you haven't ringed at a site for some time, and 18 birds were caught within 20 minutes of the net going up. The catching rate remained fairly brisk despite a bit of a breeze developing and a total of 50 birds were caught in a little over two hours. Not bad going for my first ringing session away from the garden this year.

This looks like a fairly standard male Goldfinch from this angle.

However, its chin was pure white and bisected the red bib.

This patch of white feathers wasn't quite symmetrical but certainly made for an interesting looking bird

Only 2 Tree Sparrows were caught but there was a flock of about 15 feeding near the net and more are likely to be caught on subsequent visits.

Ringing totals for 18/02/2019 were: Blue Tit 8; Great Tit 2; Long-tailed Tit 2; Song Thrush 1; Robin 3; House Sparrow 1; Tree Sparrow 2; Dunnock 6; Chaffinch 2; Goldfinch 23.

Returning Black-heads

No lotions, potions or squeezing required in this case as the returning Black-heads, as you will have realised, are Black-headed Gulls. I started checking the gulls that come to bread at Orrell Water Park back in October and I was really pleased to find IA141745 was present on 08/10/2018. This bird was ringed as an adult on 29/04/2012 at Bohmke und Werder, Germany, near the Baltic coast and border with Poland, and has been recorded at Orrell Water Park each winter since then.

Black-headed Gull IA141745 back for its 5th winter.
This photograph was taken yesterday but it has been present since 08/10/2018, at least.

The next ringed Black-head to return was photographed on 29/10/18 and was another German bird. This bird was originally ringed as a nestling on 10/06/2016 at Esterweger Dose, Weser-Ems in north-west Germany and was previously recorded at Orrell Water Park from 02/10/2017 to 17/03/2018.

Black-headed Gull 5437612
Photographed on 29/10/2018 and recorded several times since, most recently on 29/11/2018.

A check of the gulls on 11/11/2018 produced another returning bird but this time it was a British ringed Black-headed Gull EZ33149. This bird was ringed as a nestling on 20/06/2017 at Elvanfoot, South Lanarkshire and was previously recorded at Orrell Water Park between 10/11/2017 and 17/03/2018.

EZ33149 just wouldn't stand still for very long so I concentrated on getting photographs of the ring rather than the bird. I only just managed to get the full number but it took 25 photographs along with a lot of cropping and some enhancement afterwards.

Only 4 ringed Black-headed Gulls were recorded at Orrell Water Park in the whole of last winter so to have 3 of them back already is a very good return rate and shows how site faithful they can be.

Icelandic Redwings & Sparrowhawks

I only had time for a brief ringing ringing session at Billinge this morning but it turned out to be well worth the effort. A total of 12 Redwings, 3 Goldcrests and 1 Sparrowhawk were caught in little more than an hour which isn't bad going for mid November, especially as only 2 nets were used. The Sparrowhawk was a new female and another that failed to do the usual last minute climb out of the net and escape trick. However, it was the fact that 3 of the Redwings were stand out examples of the Icelandic race, coburni, that made it particularly worthwhile.

The upperparts of Icelandic Redwings tend to be a shade darker overall but it is the much heavier (blotchier) and more extensive streaking of the underparts, dark brown legs and toes, and well marked under-tail coverts that make them really stand out from continental birds (nominate race iliacus).

Icelandic birds average bigger too but in my experience wing length is of limited value as most will fall in the overlap between the two races. This bird had a wing length of 126.5 mm and was noticeably bulkier than the iliacus that were caught at the same time. However, it still falls within the overlap as iliacus can have a wing length of up to 129 mm (yes 129 mm and I have caught one that big myself) although most publications used by ringers only give an upper limit of 126, 127 or 128 mm. 

November and mid November in particular seems to be a good time for Icelandic Redwings at Billinge; my first were recorded in mid November 2014 (link here)

Today's 1cy female Sparrowhawk was the 4th female of the autumn.

While on the subject of Sparrowhawks I managed to get a photograph of a cracking little male that caught a Goldfinch in the garden a few days ago. It was already wearing a ring and I was able to read part of the number which suggests it is one that I ringed at Billinge in autumn 2015 but that is as far as I could narrow it down.

Male Sparrowhawk 12/11/2018

Easterly winds have set in and are forecast to continue for a good few days so it will be interesting to see if they bring anything unusual this way. They could pep up thrush movements initially, if nothing else. I just hope they are not too strong and give me the chance to get some nets up.

Collybita, abietinus or tristis: the Chiffchaff conundrum.

Regular readers of the blog may remember that I caught a very interesting looking Chiffchaff back in September (link here). Its largely greyish-green and white livery was very different to the standard olive-green and mustard-yellow of the nominate race (collybita) Chiffchaffs that I normally catch in autumn. I thought it was likely to be a Chiffchaff of the race abietinus (the range of which includes large parts of Scandinavia, parts of eastern Europe and European Russia) but, as I commented in that earlier post, I also thought it had a look about it that potentially gave it more easterly credentials, although the early date (23/09/2018) seemed to make that unlikely.


Luckily I was able to salvage a few small feathers that it dropped in a bird bag and submitted them to Professor Martin Collinson for DNA analysis. I was certain that it would prove to be a very interesting individual whatever the result of the DNA analysis turned out to be:

1. It would be very interesting if it turned out to be collybita simply because its appearance is so unlike that of collybita.
2. It would be equally if not more interesting if it proved to be abietinus as very few have been confirmed by DNA in western Europe and also because there had been no easterly winds up to that point in September to help drift a migrant of such origin to the UK (especially the west side of the UK).
3. It would also be very interesting (if not remarkable) if it was shown to have tristis origins because of the early date, again because there had been no easterly winds up to that point in September and because its abietinus like appearance would point to it being a abietinus x tristis hybrid.

Greyish-green and white Chiffchaff caught at Billinge 23/09/2018.
Unfortunately it was not heard to call so there were no clues there. Its appearance most closely matches the descriptions for abietinus but I also knew the identification of abietinus was not necessarily that straightforward. A genetic study of migrant Chiffchaffs caught in the Netherlands found that all 23 of the birds that were identified by ringers as being abietinus, based on their appearance, turned out to have tristis mtDNA (de Knijff et al.)

The flanks were washed with pale brown similar to a tea or coffee stain on a white cloth.

The belly, breast and throat were largely white. The undertail coverts were similar to the flanks but there was a stronger buff to yellowish-buff suffusion around the vent.

The supercillium had yellow tones above and in front of the eye but was pale brown and much less distinct behind the eye. 

To say the result was eagerly awaited is a bit of an understatement and my interest was heightened after reading a paper on the genetics of Chiffchaffs caught in Britain and Ireland (Collinson et al.) that was published in British Birds earlier this year (link here). That paper looked at the genetics of 149 migrant and wintering Chiffchaffs caught during 2009 - 2017. It was interesting to see that only 9 birds in that study were found to have abietinus mtDNA and only one of those 9 was actually identified as abietinus by the ringer with the other 8 being tentatively identified as collybita or at least 'not tristis'. As for timing of autumn occurrences the few abietinus were within the same period that tristis were found with the earliest of either race being a tristis caught on the Isle of May on 28/09/2015. The study also found one Chiffchaff that was submitted as a potential tristis actually had collybita mtDNA, however, its quite dull grey appearance was considered to be unlike any of the Chiffchaff races and it was suggested that it was an aberrantly plumaged collybita.

Well I didn't have to wait too long to get the DNA result and I received an email from Thom Shannon, a PhD student working with Martin Collinson, saying that the mtDNA they recovered was that of a tristis Chiffchaff. Thom also commented that the plumage was a much better fit for an abietinus type and that they were of the opinion that it was a clear abietinus/tristis intergrade. As I said earlier the result was going to be interesting whichever way it went and to my mind the combination of its abietinus type appearance, its tristis mtDNA and the early date is the most intriguing outcome of all. 

For those of you that may not know mtDNA is only inherited through the maternal line so it only tells us that its Mum, Grandma or a direct female relative further back through the generations was a 'pure' tristis Chiffchaff. There is no way of knowing from the mtDNA or the bird's appearance if its genetic make-up is more tristis than abietinus or vice versa. Some may be tempted to think it is more abietinus than tristis because its appearance is a much better fit for abietinus but genetic studies on the breeding grounds have shown that is not necessarily the case (Shipilina et al.; Marova et al.). In those studies some birds with abietinus morphology (appearance) were found to have tristis mtDNA and a predominance of tristis DNA overall.

So the mismatch between the Billinge bird's appearance and its mtDNA points to it being an abietinus/tristis intergrade (hybrid) and one thing we can we can say with some certainty about such intergrades is where they originate. The contact zone (the area where the two races meet and overlap) is a relatively narrow band running from the southern Urals northwards to the White Sea and genetic studies have shown that past and ongoing hybridisation occurs in this area and that a similar mismatch of appearance and mtDNA is not found in other parts of either subspecies breeding range (Marova et al and Shipilina et al). Therefore, it is reasonable to conclude that this particular bird originated in that contact zone and will have travelled around 3250 km to reach Billinge.


Approximate zone of contact between abietinus and tristis (redrawn from Shipilina et al. and Marova et al.) and location of the site where the bird was caught.

There are other aspects to this record that make it particularly interesting with the early date being one of them. The Billinge bird is a week earlier than the earliest tristis identified in genetic study by Collinson et al and if you factor in the westerly location and absence of easterly winds up to that point in September it makes that early date even more exceptional. We will never know when it actually arrived in the UK but it was presumably at least a day or two before the capture date at Billinge, if not longer. In addition, it is a bird that calls into question what we know or think we know about the likelihood of abietinus occurring in western Europe and the UK in particular. I appreciate it is not safe to draw any firm conclusions from just one individual but if abietinus is the regular, if relatively scarce, passage migrant it is generally thought to be then the Billinge bird should have had a much greater chance of being found to have abietinus mtDNA as opposed to the tristis mtDNA that was found.

I am no expert on the subject but I would have thought there are far more 'pure' abietinus in this world (birds with abietinus appearance and abietinus mtDNA) than there are abietinus looking hybrids that have tristis mtDNA, especially when you consider the large range that abietinus occupies west of the overlap zone and the relatively small area of overlap zone itself, where all abietinus x tristis intergrades are thought to originate. It has been suggested, by some who know far more about this subject than me, that many abietinus are so similar to collybita that they probably go unnoticed in western Europe but even if that is the case I would have still thought that should leave enough abietinus that look sufficiently different to be picked out with relative ease, at least in the hand if not in the field. More importantly I would have also thought it more likely that those abietinus that can be identified from their appearance should still outnumber abietinus/tristis intergrades with abietinus morphology, assuming they are the regular and more common passage migrant that presumed wisdom suggests.

As I said earlier it is not safe to draw any conclusions from one individual but the Billinge bird is another record that adds to the uncertainty that surrounds the true status of abietinus as a migrant to the UK. In addition it extends the period when birds of tristis origin can occur and, if nothing else, is simply a very interesting record in its own right as we can be reasonably certain of the region it came from.

References:
Collinson, J.M., Murcia, A., Ladeira, G., Dewars, K., Roberts, F. & Shannon, T. 2018. Siberian and Scandinavian Common Chiffchaffs in Britain and Ireland - a genetic study. British Birds 111: 384-394.

Shipilina, D., Serbyn, M., Ivanitskii, V., Marova, I. &  Backström, N. 2017. Patterns of genetic, phenotypic, and acoustic variation across a chiffchaff (Phylloscopus collybita abietinus/tristis) hybrid zone. Ecology and Evolution 2017; 1–12.

Marova, I.M.,Shipilina, D., Federov, V., Alekseev, V. & Ivanitskii, V. 2017. Interaction between Common and Siberian Chiffchaff in a contact zone. Ornis Fennica 94: 66-81.

de Knijff, P., van der Spek, V. & Fisher, J. 2012. Genetic identity of grey chiffchaffs trapped in the Netherlands in autumns of 2009 - 2011. Dutch Birding 34: 386-392.