Sinensis Cormorant 27/02/2018

There was a good covering of snow first thing this morning so I decided to go out and enjoy it by giving the dogs an early walk. I took my usual route through Orrell Water Park and was surprised to find the lakes largely free of ice, especially as the forecast had predicted the overnight temperature to fall well below freezing. Anyway the local waterfowl weren't complaining and they had been joined by a couple of Cormorants, one of which was a cracking example of the subspecies sinensis.

While I have seen plenty of sinensis at other sites over the years this is the first one I have knowingly encountered at Orrell Water Park, so it was a patch tick of sorts. The lakes at the park are quite small and cormorants don't drop in that often or stay for very long and when they do it is usually only single birds, so seeing two together and having the opportunity to have a good look at them is quite unusual. I didn't have my camera with me while I was out with the dogs but luckily they stayed around long enough for me to get a few record shots afterwards.

A nice comparison shot of a carbo left and the sinensis right.

While there is a striking difference in extent of the white head plumes of these two birds it is the angle of the gular patch that is a more reliable feature for separating sinensis from carbo. The angle ranges between 38° and 72° in carbo and between 66° and 111° in sinensis (Newson et al). The angle on the white headed bird is clearly more than 90° and confirms it as a sinensis. It is also smaller than the carbo, having a noticeably smaller head and bill and more slender neck, which is typical of sinensis.

It is a smart looking bird.

It looks like it will get cold enough to freeze the lakes over in the coming days and with the whole of the country and much of Europe in the grip of this cold spell it could be an interesting few days. I will certainly be doing my bit to monitor its effects on the birds and other wildlife around here.



References:
Newson, S., Hughes, B., Russell, I., Ekins, G. and Sellers, R. (2004) Sub-specific differentiation and distribution of Great Cormorants Phalacrocorax carbo in Europe. Ardea 92, 3–9

Curly claws, pigeon porn and other garden goings on.

I was photographing birds in the garden yesterday afternoon when I noticed a Goldfinch that was sat belly down on a branch. It had its back to me but its abnormal posture clearly indicated that something was wrong. At first I thought it was a sickly individual, perhaps suffering from trichomonosis, but then I realised it had abnormally long claws and couldn't grip the branch normally.

I eventually managed to get some photos of it face on and apart from its feet it appears to be in good condition.

I have occasionally come across birds with overgrown bills but it is more unusual to see birds with hugely overgrown claws. It obviously had some form of skin condition affecting its feet, possibly knemidocoptic mange, and this has presumably led to the overgrowth of the claws. It was able to use the feeders that have perches but the state of its feet must impede it when more acrobatic feeding methods are required. Diseases that affect birds feet are becoming an increasing health issue for birds that are attracted to garden and other feeding stations with Chaffinches being the most affected species.

As for the pigeon porn, it was, as you may have guessed, just a pair of Woodpigeons mating. It is quite early for them to be breeding but then a pair of Woodpigeons usually manages to rear an early brood near the garden. I have seen recently fledged young in early to mid April in previous years and allowing for a nestling period of about 33 days and and incubation period of 17 days that gives a first egg date in mid to late February, so this pair is continuing that early breeding trend.

Mating Woodpigeons. Spring was certainly in the air for this pair.

The last week has seen a increase in the number of Siskins visiting the garden feeders, not a big increase but a noticeable one nevertheless. I still haven't seen more than 10 at the feeders at any one time but the varying proportions of males and females along with ringed and unringed birds shows there is quite a bit of turnover during the course of a day. In addition, recent ringing activity has produced 16 new birds and photography has shown that some of the savvy returning ringed birds are still present and avoiding recapture. However, the most obvious sign of the higher numbers has been the increase in the volume of chatter coming from the birds when they sit in the tops of the trees between bouts of feeding.

Almost two thirds of the Siskins caught this winter have been adults which suggests they didn't have a particularly good breeding season last year.

Although I wasn't able to get the full ring number this bird is almost certainly one that was ringed in the garden last winter or early spring.

Long-tailed Tits are still regular visitors but the flocks have largely split into pairs now. With some very cold temperatures forecast for the next week it will be interesting to see if any of the flocks reform temporarily or if they remain in pairs.

I managed to read just enough of this bird's ring number to be able to say that this one was ringed during the winter of 2014/15.

Robins don't feature in the blog very often but an unringed bird appeared to be a newcomer to the garden and was doing its best to assert its place in the pecking order. There was a lot more in the way of chasing than I have seen of late and it seemed to have claimed top slot by the end of yesterday. Its reign may only be temporary though as there is likely to be a lot more competition and far more aggression between the local Robins as we move into the spring.

Cock Robin 22/02/17.

Goldcrests have been regulars at the feeders this winter and, even though there is usually only one bird in attendance, ringing has shown that four birds have acquired the habit of feeding on the fat cakes and fragments of sunflower hearts.

Lastly, a Wren has also taken to feeding on the fat cakes and is a frequent visitor to the fat cake in the bird table trap. It is free to come and go as often as it likes as the trap has a manually operated door that is left open and is only used very selectively.

For the record all of the photos were taken through double glazing which does have an effect on image quality, well that is my excuse. I have come to the conclusion that it is better to make that compromise on image quality rather than risk missing out on photo opportunities and adding to global warming by leaving the windows wide open for hours at a time. That's all for now and I hope you found something of interest.

Recoveries

Details of the Helgoland scheme Black-headed Gull came through recently. It has become a regular at Orrell Water Park since the first sighting last October and has been recorded a total of 17 times up to 9th February.

Black-headed Gull       DEW 5437612
Nestling                       10-Jun-2016       Esterweger Dose, Weser-Ems, Germany
Ring read in field         02-Oct-2017       near Orrell, Greater Manchester, UK
Ring read in field         09-Feb-2018      near Orrell, Greater Manchester, UK
Duration: 609 days      Distance: 688 km       Direction: W

Black-headed Gull 5437612 photographed 09/02/18

The Hiddensee scheme Black-headed Gull IA141745 has featured in this blog many times before and has been a regular at Orrell Water Park again this winter. It was first recorded in autumn 2012 and has been recorded each autumn/winter since then. It has now been sighted on a total of 83 occasions up to 09/02/18 and is possibly one of the most photographed Black-headed Gulls in the UK as a result.

Black-headed Gull        DEH IA141745
Full grown male            29-Apr-2012      Bohmke und Werder, Mecklenburg - Vorpommern, Germany
Ring read in field          27-Oct-2012      near Orrell, Greater Manchester, UK
Ring read in field          09-Feb-2018      near Orrell, Greater Manchester, UK
Duration: 2112 days     Distance: 1102 km      Direction: W

Black-headed Gull IA141745 photographed 09/02/18

British ringed Black-headed Gull EZ33149 has been another regular at Orrell Water Park this winter and has been recorded on 8 occasions so far (first and most recent date given below).

Black-headed Gull        EZ33149
Nestling                        20-Jun-2017      Elvanfoot, South Lanarkshire, UK
Ring read in field          10-Nov-2017     near Orrell, Greater Manchester, UK
Ring read in field          09-Feb-2018     near Orrell, Greater Manchester, UK
Duration: 234 days       Distance: 222 km       Direction: SSE

Black-headed Gull EZ33149 photographed 09/02/18

                                                                                                            


A Lesser Redpoll controlled at Billinge last October had been ringed just 5 days earlier but the details only came through a little earlier this year. It is unusual in that it had moved in the opposite direction to that usually expected in autumn and the movement is made even more intriguing because it involved an adult.

Lesser Redpoll             S341203
Adult female                 26-Oct-2017     Lichfield Block, Cannock Chase, Staffordshire, UK
Caught by ringer          31-Oct-2017     Billinge Hill, near Billinge, Merseyside, UK
Duration: 5 days           Distance: 94 km          Direction: NNW

Adult female Lesser Redpoll S341203 photographed 31/10/17

                                                                                                            

A Siskin that was ringed in my garden on 14th April 2016, a relatively late spring date for the garden, was caught by a ringer in western Scotland just a few days ago. Siskins migrate more in some years than others in response to the availability of food and this bird has clearly been able to stay much further north this winter.

Siskin                           S144891
2CY Male                     14-Apr-2016      near Orrell, Greater Manchester, UK
Caught by ringer          11-Feb-2018      Kilmartin, Argyll and Bute, UK
Duration: 668 days       Distance: 339 km       Direction: NNW

                                                                                                                           

Lastly, a Yellowhammer was recovered after falling prey to a Sparrowhawk. It hadn't moved far as is to be expected from this largely sedentary species but it still provides valuable information on lifespan along with timing and cause of death. 

Yellowhammer             TP63714
Adult male                   24-Jul-2014      Billinge Hill, near Billinge, Merseyside, UK
Predated                     25-Jan-2018     Houghwood Golf Course, Billinge Hill, Merseyside
Killed by Sparrowhawk under pheasant feeder.

Duration: 1281 days    Distance: 2 km           Direction: W

Siberian Chiffchaff inside and out ???

Regular readers of the blog may remember that I posted details of a Siberian Chiffchaff (P. c. tristis) caught at Billinge on 17/11/2017 and that I said it may not be the last time you would hear about about it (link here). It was an interesting looking bird and did have a trace of yellow in the supercillium, just above the eye, which 'classic' tristis is not supposed to have but its call was spot on for tristis. Being aware of some of the ongoing debate about the plumage limits of tristis I contacted Martin Collinson to see if he would be willing to undertake DNA analysis of a couple of small body feathers it had dropped, which he kindly agreed to do. I hoped having the birds DNA analysed would confirm its identity and help inform the debate surrounding the appearance of tristis type Chiffchaffs that reach our shores.

I received the results of the DNA analysis last week and it was an unequivocal result for tristis. Unfortunately that isn't quite the slam dunk the average person tends to associate with DNA results these days. The result came from an analysis of the mtDNA (mitochondrial DNA) which is commonly used for confirming the identity of bird species and is usually conclusive. However, mtDNA is only inherited through the female line and doesn't always tell the whole story where subspecies and possible hybridisation are concerned.

mtDNA result for the Billinge bird (lab reference CC243 tristis)

I have done a lot of reading up on the issues surrounding the identification of Siberian Chiffchaff since catching the bird and I think I have got my head around the current state of play, more or less. There is a lot of information and opinion out there on the web but the best 'one stop shop' that gives a thorough account of the issues surrounding the identification of Siberian Chiffchaffs can be found on Alan R. Dean's website (link here). This site gives the most comprehensive and authoritative discussion of the subject that I have come across and provides links to and or references just about everything that is worth reading on the subject if you want to delve even deeper. The text is inevitably lengthy and quite technical so if you are not familiar with terms like allopatry, sympatry, morphotypes, haplotypes and the like then you will find helpful if you brush up on their meaning first. The terms 'fulvescens' and 'riphaeus' are also used for birds of particular plumage types but an explanation of their origin and how they are currently used is given.

At this point it is worth having another look at the bird and, as noted earlier, it has a slight trace of yellow in the supercilium just above the eye. The images also show the fringes of the remiges (flight feathers to you and me) and wing coverts are olive green, and that there is a slight olive cast running into the edges of an otherwise greyish-brown mantle. There is no yellow on the underparts with the belly and lower breast being white. The undertail coverts have a buff wash, stronger towards the vent, while the flanks have more of khaki wash but with a buffish tinge running through. The upper breast had a slight khaki wash which increased in strength towards the sides.

The trace of yellow in the supercillium above the eye was only noticeable on close inspection and couldn't be detected when the bird was held at arms length.

The ear coverts have a distinct rufous tinge which is often considered a hallmark of 'classic' tristis. The crown, nape and upper mantle are an unadulterated greyish-brown.

The rufous tinge to the ear coverts is even stronger in this image.

So what are my thoughts on the Billinge bird now? well I am still happy it is a tristis. It doesn't meet all the plumage criteria for what are termed 'classic' tristis but it only falls down on that trace of yellow in the supercillium and the touches of olive running into the edge of the mantle, both of which wouldn't have been noticeable in the field. It closely matches birds described by Dean as non-classic Siberian Chiffchaffs ('fulvescens') that occur in the allopatric West Siberian plain (link here) but it is also possible, and some may consider just as likely, that it is a 'fulvescens' type bird from the the overlap zone between abietinus and tristis, which runs from the southern Ural Mountains to the Archangelsk region. Either way it had travelled a long way to get to Billinge, around 3,500km in the case of the overlap zone and at least 4,000km if from the West Siberian Plain.

Is it 100% tristis? well that is a different matter altogether and the simple answer I don't know and the only way to find out would be an analysis of the whole genome. The recent research by Shipilina et al involved analysis of whole genome sequence data and has shown that there are varying degrees of genetic admixing in the overlap zone and confirms there is some hybridisation between abietinus and tristis in that area. That study and another by Morova et al also points to genetic mixing being the underlying cause of variation in plumage traits, mixed vocalisations and reaction to each others typical song. Their findings also show that some birds from the overlap zone that looked like 'pure' examples of tristis and abietinus did in fact harbour some genetic material of the other, although this was less frequent and to a much lesser extent in the tristis examples.

The traces of yellow and olive seen in 'fulvescens' type birds from the West Siberian Plain may prove to be a result of there being a touch of abietinus somewhere in their distant ancestry, although that is purely conjecture at this stage. The genetic legacy of historic hybridisation may get diluted to a large degree over time but can be very persistent, as is aptly shown by the small percentage of Neanderthal DNA that can be found in all people of European origin even though Neanderthals became extinct about 40,000 years ago.

Finally, while I can't say it is a 100% thoroughbred tristis I am more than happy it is sufficiently tristis, inside and out, to be classed as one.


Acknowledgements:
Thanks to Martin Collinson and his team for undertaking the mtDNA analysis of the feather sample.

References:
Dean, A.R. 2009.  'Siberian Chiffchaff' Phylloscopus collybita tristis: discussion and photo gallery. http://deanar.org.uk/tristis/tristis.htm  (With updates to 2017, including the significant 'whole genome sequence data' established by Shipilina et al. 2017)

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., Shipilina, D., Fedorov, V,. Alekseev, V. & Ivanitskii, V. 2017. Interaction between Common and Siberian Chiffchaffin a contact zone.  Ornis Fennica 94: 66–81.

Savvy Siskins and Sneaky Snipe

In an previous post I mentioned how Siskins had started visiting the feeders in my garden much earlier than usual this winter and that the first two seen in late November were already ringed. I speculated that both were likely to be returning birds rather than having been ringed elsewhere and I thought I would be able to confirm that by retrapping one or both of them within a relatively short space of time. I have caught 11 Siskins in the garden since then and over 100 Goldfinches but haven't caught either of those ringed Siskins, both of which were adult males, or any others that had been ringed prior to this winter, let alone ringed elsewhere. Now that I have ringed some Siskins this winter it isn't possible to say a bird could be a returnee by the mere presence of a ring as I was able to with those first two males.

It is fair to say that I am both surprised and disappointed that I haven't retrapped either of those ringed Siskins and that disappointment has been compounded by two I have photographed recently. I have got loads of photos of Siskins, some of which are really quite good, but that doesn't stop me from trying to take more, and I have done a bit of 'snapping' over the last week or so. When I review photographs I always look to see if I can read any rings, if present, and I managed to read part of the ring numbers of a couple of Siskins and, surprise surprise, they weren't birds I had ringed this winter. The first, a male photographed on 24th Jan, was wearing ring that started Z0..... which is the start of a sequence that I was using in the garden 2 to 3 years ago and certainly not this winter. The second was a female with a ring inscription that started with the letter S...... and another photo showed more of that ring number which pointed to it having been ringed in the garden last January.

Z0........ male Siskin

The other photos of this bird revealed more of the ring number which, by a process of elimination, is almost certainly a bird that was ringed as an adult female on 22/01/2017

I have no way of knowing how long they have been visiting the feeders but there is a chance the Z0....... ringed bird could have been one of those initial males. What I can say is that at least 3 Siskins, ringed prior to this winter, have visited the feeders and that all 3 have evaded recapture to date. Their ability to avoid being caught strengthens my view that they are all returning birds and that they are quite savvy when it comes to avoiding a mist-net in my garden because they have seen it all before. Net shyness, as it is sometimes referred to, is not unusual and is most common in resident birds or at times when a population becomes relatively static such as birds visiting feeders in winter and is something I try to minimise in various ways, so it is interesting that these Siskins appear to have remembered or perhaps I should say retained that level awareness despite being away from the garden for over 7 months. Obviously there is still a chance that these birds will end up being caught at some point later this winter but I wouldn't like to bet on it.

Regular readers of this blog may remember some photographs of Snipe roosting in a field of winter cereal that I posted on the blog last winter (link here). Snipe roosted in this field from November (when they were first found and up to 29 were counted) through to at least mid-January (when the crop started to grow and made the birds harder to see). I had never seen Snipe using an arable crop as a daytime roost site before and, knowing how traditional Snipe roosts usually are, I wondered if they would use the field again, especially if the type of crop changed. As things turned out the field was sown with rape in the autumn and I thought that change, and the fact that rape has a different structure, can get denser and a bit taller than autumn sown cereals during the winter, may put the birds off.

I didn't spot any birds using the field during November and the density of the crop meant any birds, if present, had a much better chance of remaining unseen, especially if they had chosen a different part of the field to roost in. It started to feel like I was looking for the proverbial needle in a haystack but I continued to scan the field from time to time. I probably could have got permission to do a walk through survey but it would have been very difficult to find a time when other people weren't around and I was concerned it may have drawn others to think it was OK to do the same, so I decided to stick with observations from the adjacent public footpaths to be on the safe side. Unfortunately there is trend for people in this area to think it is OK to walk around the headland of just about every field and even walk through crops with their dogs rather than sticking to the numerous public footpaths and public open spaces.

Anyway, I happened to be scanning the field about a week ago, on one of this year's rare sunny days, when I noticed a Snipe amongst the rape and it was in the same part of the field that the birds used last winter. Further observations revealed a few more and I eventually counted 10. A few days later I could see a similar number in the same area when a loud bang and some crashing from a building site about half a mile away caused a few more birds to pop their heads up and I ended up counting a minimum of 19. Unfortunately I didn't have my camera with me on either occasion but I have managed to get some images since.

The images above give you an idea of how difficult the are to see but it gets a bit easier once you get your eye in. I am sure they have been using the field all winter and that I have simply overlooked them until recently. If you think they were quite difficult but want a real challenge have a look at the series of images below. 

Spot the Snipe, not that you have any chance of finding it in this photo.

Try again in this zoomed and cropped image but I wouldn't waste too much time trying.

Same image again but even with a nice red arrow pointing it out you will probably struggle to see anything identifiable as a Snipe.

.....and here is a tighter crop of the same image and you can just see the distinctive crown stripes of a Snipe's head. Now that was a difficult one.

I certainly believe the use of this field by Snipe in successive winters qualifies it as a traditional roost site (and Snipe could have been using it prior to last winter) but it remains to be seen how long this particular winter roosting tradition can survive in the face of modern agricultural practices and crop rotations.

Garden Ringing: 20th January 2018

The weather hasn't been suitable for mist-netting over the last week or so but yesterday morning presented a brief opportunity ahead of a belt of rain that was due to move in. I set up the usual 6 metre net in the garden shortly after first light and caught 22 birds in just over an hour before the forecast rain put a halt to proceedings. The catch was much as expected with Goldfinches accounting for the majority of birds caught and another 2 new Siskins continued the early presence of that species in the garden.

The light was shocking yesterday (that is why it was so good for mist-netting) so this and the following photos of finches were from a few days ago.

Female Siskin being photobombed by a Goldfinch (also a female).

........and again.

That could have been that but the rain stopped towards mid-afternoon when I caught 2 Starlings in the manually operated bird table trap with one being a new bird and the other a retrap. I try to avoid recapturing colour-ringed birds but now and again the opportunity to catch a new bird takes precedence. The new bird had a full yellow bill which was well ahead of a lot of the other Starlings seen or caught recently. This bill colour change often goes unnoticed but the predominantly yellow colour of the adult bill changes to black towards the end of the breeding season, generally starting in late June or July, and juveniles start life with an all dark bill. The change back to the yellow bill of the breeding season can begin as early as November in the British population and generally a bit later in migrants from the continent and there are also differences between age classes with older birds generally changing first.

Male Starling ringed 29/11/17. Note the bill is starting to change from black to yellow and the base is becoming blue, showing it is a male. The uniform eye colour also indicates this bird is a male.

Female Starling ringed 20/01/18. The bill is all yellow and the base is turning pink showing this bird is a female. The pale eye ring also confirms the sex as female.

The ringing didn't end with a couple of Starlings as I decided to put the net up again because the weather conditions were perfect (very overcast and no wind) and the forecast for the next week was looking pretty dire. The net hadn't been up for more than ten minutes before another 10 Goldfinches had been caught and another half hour saw the afternoon total rise to 17, all Goldfinches (16 new and only 1 retrap). I could have carried on but I decided to call it a day as I was more that satisfied with a day total of  35 new birds and 6 retraps plus I had other things to do. Final ringing totals for the day (retraps in brackets) were: Goldfinch 29 (4); Chaffinch 2; Siskin 2; Greenfinch 1; Starling 1 (1); Coal tit (1).

Now you may have noticed that the ringing totals aren't listed in any sort of species order but my thoughts on that and recent changes to the British List can wait until another day, but the one thing that should really stand out is the lack of tits. There are very few Blue, Great and Coal Tits visiting my feeders and it has been pretty much the same all winter, but more so since the turn of the year. I don't know if it is because their populations are particularly low or if there is plenty of natural food that has allowed them to stay closer to their woodland breeding sites but there is no doubt that my garden is generally devoid of tits, apart from periodic visits by the Long-tailed variety. I am not complaining as I am not what you would call a tit man (can you say that anymore in these overly PC days) but Blues and Greats seem to have been unusually scarce in the garden this winter.

Long-tailed Tit feeding behaviour.

Way back in December 2013, the 24th to be precise, I was watching birds visiting the feeders in the garden when I noticed a Long-tailed Tit hanging from a twig by one leg whilst holding a sunflower heart in the foot of the free leg and feeding on it. I had never seen a Long-tailed Tit feeding on a sunflower heart in this manner before and I couldn't find any descriptions or reports of this behaviour in the literature I had to hand or from internet searches. I posted a brief account of what I had seen on the blog at the time and a link to that post can be found here.

It didn't appear to be common behaviour amongst the many Long-tailed Tits visiting the garden back then and although I observed this feeding behaviour on more than one occasion later that winter it may have been limited to just one individual. This was one of those situations when it would have been really informative if the Long-tailed Tits were colour-ringed as I would have been able to establish how many individuals were involved but what I can say is I didn't see more than one bird feeding in this manner at the same time.

I have seen and photographed Long-tailed Tits using this feeding method each winter since that first encounter and it has gradually become more common amongst the birds that visit the garden. I haven't started colour-ringing my Long-tailed Tits (yet) so it is still not possible to be certain of the number of individuals involved but last weekend (13th & 14th Jan) at least 4 were using the 'hanging and holding' feeding method simultaneously out of a total of ten or so that were in the garden at that time. Establishing numbers is further complicated by the fact that more than one Long-tailed Tit flock may visit the garden over the course of a day and birds from the same flock may switch between feeding on sunflower hearts and fat cakes but there is no doubt it has become more prevalent amongst the the birds that visit my garden. This also begs the question as to what extent it is an innate skill as opposed to having to be learned. Again colour-ring could help answer that as it could show if there are any differences between age groups (potentially a nice line of research for someone).

There is a bit more to it than just hanging upside down and eating - a Long-tailed Tit will take a sunflower heart from the feeder and carry it in its bill to a suitable twig and then hang upside down before transferring the seed to one of its feet. Now I don't know if individuals have a preference over which foot they hang from and which foot they hold the seed in or if they can be ambipedal but I have seen individuals hang from either foot and photos in this post show that (now there is another research project for someone). The twig that an individual chooses to hang from may be near the feeder but is often one or two metres away, presumably to avoid disturbance from larger species that may come to use the feeder. The twig selected obviously has to be a suitable diameter to enable the bird to get a good grip and the way the tendons work in the birds leg and foot probably allows it to hang with little or no effort.

There are a couple of aspects of this feeding behaviour that I find really interesting, one is that they seem to be increasingly taking advantage of a relatively new food source in the form of sunflower hearts and the other is the question of how common and widespread it has become. With that in mind I contacted Kate Risely, who runs the BTO Garden Birdwatch project, to see if it was something she was aware of and if had been reported before. Kate wasn't aware of any reports of this behaviour and thought it was interesting enough to try and find out how common and widespread it is by putting a request out on Twitter (link here). 

Kate also did a little digging and kindly pointed me to some references in the literature on Long-tailed Tits feeding whilst holding food items in one foot and hanging from the other. Two of them were notes in British Birds, one from 1959 and the other from 1989, and related to food items that had been provided. Ornithologist Derek Goodwin commented on the latter report saying: 'this is normal and usual behaviour if a Long-tailed Tit finds an insect too big to be swallowed immediately'. This shows the feeding method itself is not that unusual, although I would say I think it is one that is easily missed or overlooked in anything other than a garden or feeding station setting as Long-tailed Tit flocks are usually always on the move. However, the use of this feeding method to exploit sunflower hearts taken from feeders does appear to be relatively new.  It remains to be seen how common and widespread it is or if it is an increasing trend as has been the experience in my garden. Early replies to the BTO tweet show it has been noted elsewhere but none make comment on how long it has been happening or if it is increasing at the locations concerned.

References:
Hall-Craggs, J (1959) British Birds 52, 21-2.
Shackleton, K (1989) British Birds 82, 373-4.