Goldcrests: interesting from head to tail

Seeing is believing sometimes and certainly is when it comes to a Goldcrest I caught earlier this month and another one I caught today. The first of the two was carrying an old injury, the likes of which I have never seen before, and the second is yet another known age adult with quite pointed tail feathers.

The first bird was caught at Billinge on 15/11/17 and appeared to be fit and healthy apart from having no skin and feathers on the rear of the skull. It was obviously an old injury as the edges of the skin than surrounded the expose portion of skull were dry and showed no signs of redness or infection. I have no idea what caused the injury but it shows how resilient such a small bird can be. It weighed 5.5g and was heavier than 6 of the 7 other Goldcrests caught that morning, 2 of which were larger males, so it was clearly doing OK. The biggest problem that this type of injury will cause is increased heat loss so while it appears to be thriving now its survival chances may be reduced as the weather gets colder, but then all Goldcrests have a tough time surviving when it comes to a cold winter.

Just looks a little ruffled from the front.

Wow! Now that is what you call a bald patch. Would you have believed a bird could survive that if you hadn't seen it.

The condition and shape of the tail feathers suggested it was an adult.

A real survivor

The second Goldcrest was a retrap that I caught in the garden this afternoon. It was a male and when I looked at the tail it certainly didn't shout adult but the bird's ring number was from a sequence I was using at the beginning of the year so it had to be one. When I looked up the original ringing details it had been ringed in the garden on 22nd January so there is no question the tail you see in the images below is that of an adult.

Tail of adult male Goldcrest caught 24/11/17

Tail of adult male Goldcrest caught 24/11/17

The outer tail feathers were a bit paler and a bit more pointed than the others but they didn't appear to be as worn or as bleached as I would expect them to be if they were feathers that hadn't been replaced in the last moult. Having said that I have never caught a Goldcrest just prior to undergoing a complete moult or seen one with two generations of feathers so I don't know how worn or bleached old tail feathers get by the time they are normally moulted, let alone a couple of months on. However, I would expect them to look very bleached and extremely worn by now, especially the outers, and be much more obvious than appears to be the case with this bird. Forgetting the outer feathers the rest are quite pointed anyway and nearer the shape many associate with juveniles rather than adults. All 3 of the known age adults I have caught recently have had quite pointed tail feathers and it wouldn't surprise me if most adults have tail feathers with a shape that falls in the intermediate range of adults and juveniles and a good number probably get incorrectly aged as juveniles rather than being left unaged.

Images of the tails of the other known age adults can be found here and here.

Life before Brian.

Well not all of life just the last couple of ringing sessions on the run up to the arrival of the latest named storm - Brian. The forecast for yesterday (20th) had looked quite good and promised a dry morning with a relatively light breeze but the reality was somewhat different. When I got up at 5am the rainfall radar showed a band of rain approaching from the west and the possibility of some light showers following on behind. It started raining not long after and to say I was not happy is an understatement as I was convinced that Redwings would be moving south in large numbers given the recent arrivals further north.

Now I like to start the day with 3 mugs of coffee so I used that time to keep an eye on the progress of the band of rain on the rainfall app and it looked like it would clear Billinge around sunrise so I decided to head out. When I arrived on site it was still raining but I set up anyway, keeping the nets closed of course, so I would be ready for a quick start when the rain cleared. The rain stopped shortly after sunrise and pretty much as the rainfall app indicated so I quickly opened the nets. It was still only half light because of the cloud cover but a few small flocks of Redwings had already started moving with all of them heading south.

The breeze was quite fresh but the net rides were sheltered by the tree cover and more importantly by higher ground which provided a significant wind shadow. The catching rate was quite good but then the number of Redwings moving wasn't bad either and both increased as the morning went on. Visibility was really quite poor at times with low cloud and occasional mizzle but it didn't stop the birds moving and around 2,000 Redwings went south over the course of the morning but that is only a rough estimate.

There were other bits and bobs moving south, not that I had time to take much notice, and there were a few Goldcrests moving through the bushes. I started packing up shortly after 11am and the next to last bird extracted from the nets was a control Goldcrest. This control Goldcrest turned out to be the most interesting bird of the morning but because of its age and tail shape rather than the fact it had been ringed elsewhere. All ringers would say that they age and sex every bird they catch with an equal amount of diligence but controls often get a little more scrutiny because another ringer may have aged and sexed it when it was first caught and the passage of time between ringing and recapture can add to the information on age if enough time has elapsed.

Goldcrests are mainly aged on the shape of the tail feathers with the adult tail being described and illustrated as being quite rounded while the tail of first-year birds are sharply pointed. Svensson's ageing and sexing guide warns against the ageing of intermediates and while it is clear on that point there is inevitably a degree of subjective interpretation. Most ringers don't get to handle many known age Goldcrests and that is where the problem lies as it is too easy to assume that adults should have quite rounded tail feathers even though that is not what Svennson and some of the other literature actually say.

So I had a control Goldcrest in my hand and on first glance the tail looked quite pointed but the tail feathers were on the broad side and quite glossy which is more indicative of adult. Had it been a new bird I may not have given it the same level of scrutiny but then that is impossible to know after the fact.  It certainly wasn't a stand out first-year, nor was it a stand out adult and with hindsight I would like to think I would have left it unaged had it been a new bird but, at the risk of being honest, I may have lent towards it being a first-year. 

When I am out ringing I frequently exchange texts with David Norman of Merseyside Ringing Group, who rings at a site 16km south of Billinge, and he recognised the ring number as being a MRG bird. It transpired that it had been ringed on the Wirral as a first-year male in October 2016 which confirmed it was over a year old. This made it more interesting as it was an adult (2y+) and its tail shape certainly reinforces the advice in Svennson that intermediates should be left unaged. It wouldn't surprise me if this tail shape is quite common in adults and it is the lack of recaptures of known age birds that limits our understanding of tail shape and ageing of this species.

Adult Goldcrest tail 20/10/17

It is not unusual for me to leave a few Goldcrests unaged but I may just start leaving a few more unaged now I have seen the tail shape of this adult.

So what should have been a good morning actually lived up to my expectations despite some very unhelpful weather. Totals for 20/10/17 were: Goldcrest 9 (1); Song Thrush 2; Blackbird 1; Redwing 50; Bullfinch 1 (1). Total: 63 new birds, 1 retrap and 1 control.

That was the 20th and the prospects for the arrival of Brian today were considerably worse but I decided to put my faith in technology (rainfall radar) and checking conditions on the ground. Yes it was forecast to be even windier but topography protected the net rides and the wind is generally that bit lighter around dawn. I only set a couple of  nets as there was a higher risk of showers in the forecast but the rainfall radar showed they fizzled out before they reached the site during the time I there (occasionally technology is wonderful).

It was amazing to see a total of around 800 Redwings and a few other birds moving into such a strong headwind, especially as a strong southerly component in the wind often kills any movement at Billinge stone dead. The Redwings generally stayed low and appeared to make good headway but a lone, higher flying, Swallow made more laboured progress and clearly struggled against the strong headwind as it battled south. 

I packed up after a couple of hours as the wind was starting to get stronger but I still managed to catch 15 birds before Brian really kicked in. Totals for 21/10/17 were Goldcrest 1; Song Thrush 1; Redwing 13.

Most of the Song Thrushes I catch at Billinge in autumn are of the the greyer continental race, philomelos and today's was no exception. The greyer rump and lower mantle contrast with the much browner tail feathers.

Billinge 28th to 31st July 2017: More adult Willow Warblers

The weather hasn't been particularly favourable but I managed to get out on the last 4 days of July. I went up to Billinge and set 3 nets in on each occasion although I had to change the net positions on some days to get adequate shelter from the breeze. The 29th provided the best conditions but the sessions on the other days were restricted by light showers and or a strengthening breeze.

I made the effort because I was curious to see how many juvenile and adult Willow Warblers I would catch and if the proportion of juveniles would increase. A total of 100 birds (92 new & 8 retraps) were caught over the four sessions and almost half  (43 new & 4 retraps) were Willow Warblers. Interestingly, the proportion of adult Willow Warblers remained relatively high with 11 out of the 47 being adults, although one had been encountered earlier in the month.

Adult Willow Warbler showing quite an extensive pure white belly.

 The total number of individual Willow Warblers handled in July ended up at 104 and of these 77 were juveniles and 27 were adults which gives a simple ratio 2.85:1. While this is the lowest ratio of juveniles to adults encountered in any July the total number of juveniles handled this July is similar to 2014 & 2015 as can be seen from the table below. 2016 seems to have been an exceptional year for juveniles as a similar pattern was found when I looked at the July totals for Chiffchaff  (2014/42, 2015/45, 2016/73, 2017/40) and Blackcap (2014/35, 2015/42, 2016/65, 2017/41). So the number of juvenile Willow Warblers encountered this July has ended up in what might be considered the 'normal' range for the site.

July Willow Warblers
Year	Juveniles	Adults	Ratio (rounded off)	Visits
2017	77	27	3:1	13
2016	101	6	16:1	13
2015	71	14	5:1	11
2014	81	9	9:1	13

A ratio of just under 3:1 is much closer to the actual productivity of Willow Warblers but that is not what I am used to seeing at this site, hence my interest being sparked by the high number of adults encountered this year. There did seem to be more adults around in the spring so better over-winter survival resulting in a higher breeding population may have played a part, although it appears to be too much of a increase to account for it all. If a much higher breeding population was part or all of the cause then it still suggests productivity is low this year as more pairs would be expected to produce more offspring unless productivity has been negatively affected in some way. There is also the possibility that some of the adults were migrants rather than local birds as some were nearing the end of their moult and many adults will start migrating just before the innermost secondaries are fully grown. Either way I have caught a lot more adults this July than usual and multiple factors may be involved. As I said in my previous post it will be interesting to see how the 2017 CES results and other surveys compare.

 

Adult Willow Warbler showing more extensive yellow across the belly and a relatively pointed tail. This bird didn't shout adult and is the sort of bird that can trip you up if you're not careful and rely too heavily on a particular feature such as the colour of the underparts. Careful examination revealed it was still in active wing moult, but only just, as can be seen in the image below. 

Primary moult was just about complete but the big give away was the inner 2 secondaries that stand out as being that bit shorter than the longest tertial. Examination from underneath showed the inner 3 had some feather sheath at their bases. It is always worth giving those inner secondaries a look as the moult usually finishes with the innermost secondary rather than the outer primaries. 

I don't operate a standardised mist-netting regime so that has to be borne in mind when looking at the figures, ringing effort, however, was reasonably consistent so I still thought the figures were worth sharing. Willow Warblers are declining across the UK with the exception of Scotland and I am lucky to have a site that still has quite a good breeding population and also attracts good numbers of passage migrants (especially for an inland site). In 2016 a total of 367 Willow Warblers were ringed at the site which, like the 2016 July totals, was significantly up on the previous 2 years (2015/256 & 2014/240) so it will be interesting to see what the total looks like at the end of this year.

Highlights amongst the other birds caught included the first Garden Warbler of the autumn. A Whitethroat was also a first for the autumn but an unusually late one at that, I don't catch many Whitethroats at the site but I've usually caught a few juveniles well before the end of the month. Goldcrest on the other hand appear to be having a good year with another 10 bringing the total for July to 19. This compares favourably with the July totals for previous years - 10 in 2016, 8 in 2015 and only 3 in 2014.

Combined ringing totals (retraps in brackets) for 28th to 31st July 2017 were: Goldcrest 10; Blue Tit 3; Great Tit 4; Chiffchaff 4(2); Willow Warbler 43(4); Blackcap 7(1); Garden Warbler 1, Whitethroat 1; Treecreeper 1; Wren 4; Song Thrush 1; Robin 2, Chaffinch 1; Bullfinch 2; Linnet 5; Goldfinch 2 (2); Reed Bunting.

Garden Warbler. A scarce passage migrant at the site with most records coming in late July and early August.

Whitethroat.  A few pairs breed at the site so I usually catch a few juveniles in July but not this year.

Fabulous forty.

It looked like there would be a few hours of suitable weather this morning but it was still a case of fingers crossed and a final check of the rainfall radar before setting off. I headed up to Billinge a little later than planned but still had the first net set up by sunrise and another two nets soon after.

We are just at the start of the main migration period for Tree Pipits and most will have gone through by the end of August so I want to get out whenever the weather looks suitable, even if it's only for a couple of hours. It is also the peak time for Willow Warbler migration so that just added to the incentive to get out this morning

Three Tree Pipits were caught in the first couple of rounds which was a really promising start but unfortunately none were caught or seen after that. A check of the rainfall radar on my phone showed that a band of heavy showers had developed to the north of the site and that may have been the reason they stopped moving.

One of today's Tree Pipits was this cracking adult.

Tree Pipit adult (left) and first year (right).
There doesn't appear to be a great deal of difference in the coverts of these two birds but the first year has paler fringes to the median coverts, greater coverts and tertials and they are more abraded. Many first years replace some median or greater coverts so there is often some contrast between the new and old feathers. However, the first year on the right hasn't replaced any of its coverts so there is no contrast to be seen in this particular individual. 

While Tree Pipits didn't move through in any number the same couldn't be said for Willow Warblers. There didn't seem to be that many around at first but the final tally of 40 new birds and 1 retrap made it the hightest total recorded at the site. It all happened quite quickly with all but 1 being caught by 09:00. The retrap Willow Warbler was originally ringed as a juvenile in July 2014 and was caught again in April 2015 but not handled again until today.

The tips of this Willow Warblers tail feathers had snapped off along the line of a fault bar.

A closer look at the tail. Fault bars are a line of weakness that can develop in feathers due to a shortage in nutrition when the feathers are growing. In extreme cases the feathers can snap along the line of weakness. There were 2 other similar examples in the Willow Warblers caught this morning.

Chiffchaff was a notable absentee today with none caught or present in the vicinity of the nets. This was quite a surprise as I expected to catch a few with so many Willow Warblers being on the move. If it hadn't been for the Willow Warblers it would have been a very quiet day although I would have been happy catching the 3 Tree Pipits on their own.

Ringing totals (retraps in brackets) for 09/08/2016 were: Blue Tit 1; Great Tit 1 (1); Long-tailed Tit 1; Willow Warblers 40 (1); Blackcap (1); Whitethroat 3; Tree Pipit 3; Goldfinch 2; Reed Bunting 1 (1). Total 52 new birds and 4 retraps.

A grey day in more ways than one.

This morning dawned very grey and it was really quite gloomy at the Billinge ringing site. Looking in all directions visibility was poor and didn't extend much beyond 2 or 3 miles shortly after sunrise, not that you could see the sun rise. In fact it looked like the site was surrounded by a bank of fog especially towards the south and west so I didn't expect much in the way of visible migration. It stayed grey and gloomy for most of the morning and only brightened up a bit when the breeze started to pick up.

I had set the usual nets up at first light and was playing Grey Wagtail on the MP3 player at one net and Goldcrest at another. It wasn't long before I heard a Grey Wagtail flying over from the north east and I was hopeful of catching it but on checking the net I was pleasantly surprised to find I had actually caught five. I extracted the birds and went on to the net with the Goldcrest lure and found I had also caught five Goldcrests; a great start to the morning.

Grey Wagtail (Motacilla cinerea). A stunning species and grey in name only.

Grey Wagtail (Motacilla cinerea). A cracking bird whichever way you look at them.

Grey Wagtails continued to feature until I packed up at 11am with a total of 15 ringed from at least 34 recorded. This is the largest Grey Wagtail movement I have ever recorded anywhere and is also the most I have ever ringed in one day but as this is my first autumn ringing at this site I don't know how unusual it will turn out to be. Having said that a friend who has watched the site for many years has never recorded anything close to that number flying over so it is likely to be an unprecedented day total. I suspect it may be a case of the MP3 lure causing some birds to be caught or call back that would otherwise have passed by unnoticed but like the record number of Tree Pipits seen and ringed last month, only time will tell.

Grey Wagtail (Motacilla cinerea). Another view showing more of the upperparts.

All the Grey Wagtails caught were first year birds and had some retained juvenile coverts.
This bird has 7 old outer greater coverts and 2 old tertials.

In this bird the outer 3 greater coverts are old juvenile feathers with the remaining greater coverts and tertials being new having been replaced in the post juvenile moult.

Grey Wagtails may have been on the move but Meadow Pipits certainly weren't, at least not in any number. One group of 9 went southwest mid-morning and a handful of presumably local birds were blogging about. Other birds on the move were two Great Spotted Woodpeckers flying very high to the north east about an hour apart, a single Tree Pipit headed south, a few Chaffinches also went south along with a few Swallows.

Ringing revealed there were more Goldcrests around than would have been recorded from the number heard calling with a total of 15 ringed. Warblers were very thin on the ground with 3 Chiffchaffs ringed and only 1 Blackcap heard tacking. This is in stark contrast to Tuesday (9th) when 10 Blackcaps, 9 Chiffchaffs and a Willow Warbler were caught. Ringing totals for the morning were - Grey Wagtail 15, Goldcrest 15, Chaffinch 6, Chiffchaff 3, Reed Bunting 3, Yellowhammer 2, Goldfinch 1.

Yellowhammer (Emberiza citrinella). This adult male was just finishing its moult and was still replacing some of the feathers of the head.

Adult male Yellowhammer (Emberiza citrinella), same bird as above. I have caught 18 this month so far but all the others have been juveniles.

Female Reed Bunting (Emberiza schoeniculs). Only 3 ringed today but small numbers have been moving through the site as indicated by the lack of any retraps.

The wind is remaining light tomorrow and there should be some cloud cover first thing so I will be out early again to see what the new day brings, hopefully it will include another good movement of Grey Wagtails.

Ageing Goldfinches: a photographic guide.

It has taken me a while to get round to writing this post but here it is for what it is worth. Goldfinches can be difficult to age at times and are even more difficult to sex. In this post I only look at ageing and it is mainly based on birds caught for ringing from September to December 2013. All the photographs labelled as adults (Euring age code 4) were retraps from previous years and therefore their age is not in question. This removes any bias towards showing photographs of birds that conform to the current published ageing criteria for adults or the risk of birds having been aged incorrectly. All the birds labelled as 1Y or juv (Euring age code 3) showed evidence of only undergoing a partial moult or hadn’t completed the partial post juvenile moult at the time of capture. Some still had obvious juvenile feathers in the red mask of the face but be aware even some adults can have a few white feathers in the face that give the impression of unmoulted juvenile feathers (usually pure white as opposed to buff).



Photo 1. 1Y Goldfinch showing a few unmoulted juvenile feathers in front of the eye.



Photo 2. 1Y Goldfinch showing 1 unmoulted juvenile feather below the eye and a few others still in pin.

Photo 3. Known adult Goldfinch with 4 pure white feathers below and  behind the eye (unusual).

When I started to photograph every Goldfinch that I caught I didn’t expect to learn as much as I have. One example being that the moult of both adults and juveniles can extend well into December with the feathers of the face being the last to be replaced. This has particular implications for sexing birds but that will be the subject of another post if I ever get round to writing it. This post has been difficult to put together and has already had several false starts. What photos do you use when you have so many to choose from and what level of knowledge do you pitch it at ? I am likely to come back to this post from time to time to add photos or statistics so it should be seen as a work in progress. Hopefully some of you, especially other ringers, may find it of interest.

Most juvenile Goldfinches in the UK only undergo a partial post juvenile moult but it is thought that a very small proportion may have a complete moult like adults. The proportion of juveniles that undergo a complete moult isn’t easy to measure but is likely to be insignificant in the UK, if it happens at all. I didn’t encounter any juveniles in active primary moult and only caught 3 (<1%) that had replaced a few central primaries. However I did find that many replaced one or more tertials and some of their tail feathers.

Photo 4. 1Y Goldfinch with all new tertials, the longest tertial is not fully grown. The new glossy black tertails contrasting with the juvenile secondary feathers.

Many juvenile (1Y) Goldfinches have 1 to 3, rarely 4 or more unmoulted old greater coverts (OGCs). These are best distinguished by the contrast in appearance of the black part of the feathers rather than the colour of the tips as illustrated in Svensson. The new (adult type) feathers have a glossy black appearance in contrast to the matt black of the juvenile feathers with the differences being a bit more obvious in males. Birds with retained old greater coverts are easy to age.




Photo 5. 1Y (Juvenile) with 2 OGCs



Photo 6. Another juvenile with 2 OGCs

Photo 7. 1Y (Juvenile) with 3 OCCs.

However, some juveniles moult all their greater coverts and I found that just under 35% of the juveniles I caught had replaced them all (sample size 94). This is a significant proportion and these birds can be more difficult to age. Some ageing guides suggest there is a contrast between the new greater coverts and the old primary coverts and alula in these birds and that (with practise) this can be used for ageing. I used to agree with that view but have found a similar level of contrast between these feathers in all the known adults and therefore it isn’t a feature that stands up to close scrutiny. Having said that it is worth checking the carpal covert as this feather frequently has a dirty buff or brown fringe at the tip in juveniles although a few may be all black like most adults. In adults this feather is generally all black but very rarely a few may have a slight greyish white fringe (never dirty buff or brown as in juveniles). This feature is more obvious when the feathers are relatively fresh, in autumn and the first half of the winter, but can last through to the spring in well marked individuals.



Photo 8. 1Y Goldfinch (Juvenile) that has moulted all the greater coverts but shows a buff fringe on the carpal covert. Most juveniles had a brown or buff fringe on the carpal covert but it could be very slight in some.



Photo 9. A tighter crop of photo 8 above. Note there is no more contrast between the  greater coverts, primary coverts and alula in this juvenile than in the adult in photo 10 below.







Photo 10. Known adult showing some contrast between the black of the greater coverts and primary coverts similar to juveniles that have replaced all their greater coverts. In addition there is contrast between the small and large feather of the alula with the large feather of the alula having a faint pale tip. This wasn't expected but was consistent in all the known adults. The difference was marked enough to make them almost look like feathers of different age.

The tail shape of juveniles is generally described as being more pointed than those of adults and that they usually show more wear. However, things are not quite that simple as you will see from the photos below. A large proportion of juveniles replace the central pair of tail feathers and some replace the outermost pair with the difference in wear and contrast between the black areas of the feathers identifying these birds (again the newer glossy black feathers contrasting with the more matt black juvenile tail feathers). A few may replace more tail feathers but it is very rare for juveniles to replace all their tail feathers (1 in 300 or less). I only caught 1 juvenile that had replaced all its tail and this bird was aged from the partial moult of its primaries. As ever with Goldfinches there is a lot of variation and more overlap in tail shape than is often appreciated or illustrated in ageing guides. 



Photo 11. 1Y (Juv) with a very pointed tail shape and all the feathers are of the same generation. There isn't much wear but the shape is the clincher. If all juveniles had tails like this ageing would be easy. In addition this bird had 1 OGC and had replaced 2 of the tertials.



Photo 12. This is where things get a bit more interesting. This is the tail of a 1Y (juv) but the shape is closer to that often illustrated for adults. This bird had replaced the central pair of tail feathers and had 3 OGCs. It had also replaced the middle tertial so there is no question that this is a juvenile.



Photo 13. Here is another 1Y (juv) tail with quite a broad and not very pointed shape. This bird had 2 OGCs confirming its age as can be seen in photo 6 above. It had only replaced the central pair of tail feather but you can't see the contrast from this angle and because of the shade from my hand.



Photo 14. Here is another example of a 1Y (juv) tail. This bird had replaced the central and outermost pairs of tail feathers. It had also replaced all its greater coverts and the innermost tertial.





Photo 15. Believe it or not this is also a 1Y (juv) tail that has worn to a very rounded shape. This bird had replaced all its greater coverts and tertials. The central pair of tail feathers had been replaced but don't stand out as being a different shape. However they were obviously newer and more glossy black in colour. Ageing as a juvenile was also supported by the extent of primary wear.

Photo 16. Here is another shot of the 1Y (juv) tail above that gives a better view of the left hand side of the tail and makes it easier to see the new and more glossy black central pair of tail feathers contrasting with the remainder of the old worn tail feathers.


The photos of the juvenile tails above are a fairly random selection and show the range of tail shapes that juveniles can display. Having an understanding of this variation is particularly important when determining the age of birds with no old greater coverts. All the photos were taken over a relatively short period in December and after the post juvenile moult is complete so it isn't a case of variation over a long period of time or before and after the post juvenile moult period. The level of wear and any contrast between new and old feathers are by far the most important things to look for when using the tail to age birds with shape being more of a secondary consideration.

So now for some photos of the tails of some known adults for comparison. All the photos below are of birds that were originally ringed in previous years and are not just birds that appear to show adult features.   

Photo 17.  Known adult. This blunt and rounded shape is what ringers generally think of as being a good adult shape but it isn't exclusive to adults as we have seen in photos 15 and 16 above in terms of general shape. However there is no obvious wear and all the feathers are of the same generation. 



Photo 18. This is towards the other end of the range of adult tail shapes being fairly pointed but with a rounded tip. Again there are no obvious signs of wear and all the tail feathers are of the same age.



Photo 19. Known adult Goldfinch tail. Similar to photo 18 above.



Photo 20. Known adult Goldfinch tail.

Photo 21. Known adult Goldfinch tail. Again similar to photos 18, 19 and 20. This is probably the most common adult tail shape. The one thing all the adults had in common was the lack of wear to the tail feathers and all the tail feathers were clearly of the same generation.

There is a footnote in Svensson that says birds with sub-terminal white spots on the outer 3 tail feathers are adult although most adults only have spots on the outer 2. This has been repeated elsewhere but is not correct. I have caught numerous juveniles with sub-terminal white spots on the outer 3 tail feathers over the years as shown below. However, there is a paper that suggests birds with 3 white sub-terminal patches can be confidently sexed as males. That will have to be discussed in a future post on sexing Goldfinches or why you shouldn't sex most Goldfinches as my findings currently seem to suggest.



Photo 22. Example of a 1Y (juv) Goldfinch with white sub-terminal spots on the outer 3 tail feathers taken at Spurn in 2006.

Photo 23. 1Y (juv) Goldfinch with white sub-terminal spots on outer 3 tail feathers. The outermost tail feathers have been replaced and have a more rounded tip but all the other tail feathers are juvenile.

Photo 24.  1Y (juv) Goldfinch with white sub-terminal patches on the outer 3 tail feathers. This bird was ringed 09/11/13 and had replaced all its greater coverts but all the tail feathers were old (juvenile).

The one ageing feature that I haven't illustrated with photographs so far is the difference in primary wear that is shown by juveniles compared to adults. The primaries are always worth checking and can be very useful for confirming a birds age. In juveniles the white tips wear quite quickly in autumn whereas adults can remain relatively fresh throughout the winter.



Photo 25. 1Y (juv) primaries showing how the white tips become quite worn and chipped by early autumn. Sometimes the white tips wear away almost completely.

Photo 26. Adult primaries still showing fresh white tips with no wear and this photo was taken a month after the juvenile above..The outer 2 primaries have a slightly lighter brownish black ground colour compared to the rest of the primaries. This is normal in both adults and juveniles and is a result of these feathers taking more of the stress when the birds are in flight. The feathers on the leading edge cut through the air and are subject to more wear, tear and bleaching as a result. The large feather of the alula fades more quickly for the same reason and explains the difference with the small feather of the alula shown in photo 10 above.

Even though I have taken a lot of photographs it is really difficult to show some of the features well as they are quite subtle. The contrast between some feathers is fairly easy to see in good light when you can keep tilting the bird to catch the light but is much more difficult to photograph. I just hope some of you find this of interest and useful as a reference.

UPDATE 01/02/14
I caught a few Goldfinches on 30/01/14 that included another known adult (ringed in 2012) along with an unringed adult and some first winter birds. This allowed me to make a direct comparisons of the relative wear of the known adult, new adult and juveniles and to see if the differences in wear were still as marked as they had been. I took the usual range of photographs and present a few reference images below.The difference in wear is slightly greater to that seen in the late autumn/early winter in these individuals with the juvenile having lost more of its white primary tips to the point where they have almost disappeared on some feathers. The adult primary tips remain complete and very fresh in comparison and this was equally true for the new adult.

Photo 27. Juv top and adult below. The difference in wear is quite marked with the white tips of the juvenile having almost completely worn away. The adult feathers still look very fresh in comparison and show no abrasion or chips. The outer 2 or 3 primaries of both birds show the more brownish black background colour discussed in the original post above (see photo 26)

Photo 28. This juv has replaced all of the greater coverts (0 OGCs) . In this individual you can see some contrast between the glossy black part of the new greater coverts and the old juv primary coverts, and alula but be aware some adults can look like this as shown and discussed above.

Photo 29. There is little or no contrast between the black part of the greater coverts and primary coverts in this known adult. However the large feather of the alula stands out as being much paler. This is just because of the additional wear and tear that feather takes in the course of normal flight and is not a case of that being an older unmoulted feather. There are no 'moult limits' in this wing.

Photo 30. Juv tail. This bird has replaced all but the 3rd and 4th outermost tail feathers. The difference in wear and shape is there to be seen but they are not huge even this far on in the winter. You do need to check every tail feather on every bird.

Photo 31. Known adult tail. All the feathers are clearly of the same age with little or no signs of wear.

D130399 was also interesting in that I hadn't caught it in the usual way. This bird flew into a window and stunned itself on 03/11/12. I kept it in a bird bag for a short time afterwards and it seemed to recover quite quickly so I ringed it prior to release. It is nice to know that birds can fully recover from such impacts.

I will update this post again later in the year (ideally March or April) if I catch any suitable retraps/known age birds that show how the plumage wear progresses.