25th July 2017: What's happened to Willow Warblers

Another ringing session in the top willows at Billinge failed to produce the sorts of numbers expected for this site in late July. It was made even more disappointing by the fact that it was my earliest start of the autumn (I got up at 04:30) and the conditions were perfect for mist-netting all morning.

The calm and overcast conditions were perfect for mist-netting. Looking in this direction on a clear day I can normally see the major landmarks of Liverpool and the Welsh mountains beyond.

There were a few more Willow Warblers around with a total of 17 (12 new & 5 retraps) being an improvement on the previous visit but almost half (8) were adults which is really unusual. To put that into context I haven't caught anywhere near that many adults in a single July session before, and in 2016 only caught 7 adults in the whole of the month.

Adult Willow Warbler

You can't read too much into a single session so I looked at the ratio of juveniles to adults caught each July over the last 3 years. This is a better guide to productivity than overall numbers as it removes any effect caused by variation in ringing effort between years. The results showed that juveniles have outnumbered adults by a least 5:1 in each of the last 3 years, and in July 2016 the ratio was just shy of 17:1. The average of the ratios for the last 3 years being just over 10:1.

Willow Warblers: juvenile left and and adult right. The juvenile shows the typical lemon yellow washed underparts whereas the adult is much whiter although this adult has more extensive white underparts than many.

Looking at the figures for this July the ratio of juveniles to adults currently stands at just under 2.5:1 which is quite worrying and suggests productivity is well down compared to previous years. There is not much of July left so even if the weather allows me to get out again before the end of the month I would have to catch 43 juveniles and no adults just to bring the ratio up to 5:1 and there seems to be little likelihood of that happening. To bring the ratio near to the average of the last 3 years I would have to catch 133 juveniles and no adults and there is simply no prospect of that. It certainly looks like Willow Warblers have had a very poor breeding season, locally at least. I say locally as most of the birds caught in July will be local breeders and their offspring. 

The prospects for this breeding season had looked quite good at one stage with with migrants, like Willow Warblers, arriving quite early and in good numbers. There is no doubt the weather over the spring and summer has been mixed but it generally seemed to be more favourable for breeding birds than the last couple of years and certainly no worse. To find that Willow Warbler productivity appears to be so low this year is totally unexpected and hard to explain. It will be interesting to see the results of CES and other BTO surveys when they come out later in the year to see how they compare.

Willow Warblers have shown marked differences in regional trends in recent years with the species showing large declines in the south and holding their own or doing better further north. Next month should see a lot of migrant Willow Warblers move through the site and their numbers may give an indication as to how the species has fared in more northerly areas of England and Scotland. Lets hope they have done better further north.

The final capture total of 40 birds (33 new and 7 retraps) was less than expected and continues to suggest that quite a few species have had a poor breeding season locally. Ringing totals for 25/07/2016 (retraps in brackets) were: Goldcrest 2; Blue Tit 5; Great Tit 1; Willow Tit (1); Chichchaff 5 (1); Willow Warbler 12 (5); Blackcap 2; Wren 1; Robin 1; Chaffinch 1; Bullfinch 1; Goldfinch 1; Reed Bunting 1.

Billinge: 22nd 2017 July

I had high high hopes for this session in the top willows by my optimism and early start wasn't rewarded. Equivalent sessions in previous years have produced good numbers of phylloscs and out of habitat migrants such as Sedge and Reed Warblers but that wasn't repeated today. The weather probably played a part as overnight rain probably put the dampers on any migration and the site was still shrouded in hill fog/low cloud when I arrived, although it soon lifted.

It turned out to be one of those days that was noteworthy for the birds that were absent or only present in low numbers and chief amongst those was Chiffchaff with only 1 recorded all morning, and that one only turned shortly before I packed up. There were fewer Blackcaps around than usual and although Willow Warblers crept into double figures a total in the high teens would have been nearer the norm. Once again, tits were few and far between and there was certainly no sign of any mixed tit/warbler flock formation. I didn't even hear any Long-tailed Tits nearby or in the distance. The only species that seemed to be present in higher numbers than usual was Wren with 5 ringed. I think Wrens should be renamed fidget spinners as this aptly describes their behaviour in a mist-net.

The final total of 32 new birds and 4 retraps wasn't bad but was lower than expected for late July. Totals for 22/07/17 (retraps in brackets) were: Great Tit 2; Willow Tit (1); Blue Tit 2; Chiffchaff 1; Willow Warbler 11 (1); Blackcap 3 (1); Treecreeper 1; Wren 5;  Robin 1; Bullfinch 3 (1); Goldfinch 2; Reed Bunting 1.

Adult Willow Warbler (all the photos below are of the same bird).
Three of the Willow Warblers were adults and two of them had almost completed their full moult.

Once the moult is completed, in probably just a few days for this individual, they start migrating back to Africa. They often start to put on fat just prior to the completion of the moult so they are ready to go with little or no delay.

Once the moult is completed Willow Warblers can only be aged by the colour of the underparts and shape and wear of the tail feathers. Adults have a white belly whereas juveniles are usually completely yellow or yellowish underneath.

Adult tail. Generally broader and less pointed and also showing less wear than the juvenile tail. The tail feathers are usually glossier too as they are newer than those of most juveniles which often look a tad browner.

Billinge: 17th & 18th July 2017

17th July
I am not getting any better at the early morning lark and only got to site at 7am. The weather was glorious and it was very warm from the off. I quickly set 3 nets in the top willows but there was distinct lack of warblers calling in the bushes which suggested there were fewer around compared to my last visit. On the other hand there had been a marked increase in the number of Goldfinches with at least 60 feeding on the knapweed in the vicinity of the net rides.

A total of 46 new birds were caught with all but one being juveniles. The single adult was a moulting female Willow Warbler. The ringing totals confirmed that there were fewer warblers around but this was offset by a good catch of Goldfinches. The biggest surprise was a near total absence of tits, not that I am complaining, with only 2 caught and hardly any others seen or heard.

Juvenile Goldfinch

One of the juvenile Goldfinches had white sub-terminal patches on the three outer tail feathers. These patches were once thought to have some age related significance and while the number of patches Goldfinches have varies between 1 and 3 the presence of 3 was considered to be something that was only found in some adults. Juveniles like the bird above clearly show that can't be the case and serve as a useful reminder. A more recent study suggested birds with 3 patches were always males and while males may have more and or bigger patches on average there is more overlap than that study found and I have caught females with 3. I am sure these tail patches have an important role as birds spread their tail and show them off when they do the clockwork like pivoting display but they are not the help we would like them to be when it comes to ageing and sexing Goldfinches in the hand.

Totals for 17/07/17 were: Goldcrest 1; Great Tit 1; Coal Tit 1; Chiffchaff 6; Willow Warbler 7; Blackcap 6; Wren 3;  Greenfinch 1; Goldfinch 20.


18th July
With thundery and then showery conditions forecast from mid-week I decided to fit in another visit and try the rides in the NE corner of the site. It was another very warm morning and the biting insects were really on form but it turned out to be very quiet on the bird front. The catching rate was really slow and I packed up at 10am, following 2 blank net rounds, and having only caught a total of 14 new birds in the earlier rounds.

Again there were hardly any tits around and warblers were also very thin on the ground for this part of the site. Tits are supposed to have had a reasonable breeding season but I haven't seen or heard any sizeable tit flocks as yet but that doesn't mean they are not out there, somewhere. It was just one of those mornings that produced a below par catch, as happens now again, and it will be a while before we really know what sort of breeding season it has been overall.

One of the Dunnocks was a recently fledged juvenile.

The flight feathers were not fully grown but it could fly quite well and was caught in the top panel of a mist net.

It will still be dependant on its parents for food so it was released very close to where it was caught.

Overhead there was no movement to speak of but a single Yellow Wagtail, a scarce bird in this area these days, went south as did a Siskin.

Ringing totals for 18/07/17 were: Goldcrest 3; Blue Tit 1; Chiffchaff 2; Willow Warbler 1; Blackcap 1; Wren 2;  Dunnock 2; Chaffinch 1; Bullfinch 1.

12th July 2017 - A bunch of Blackcaps

I only managed a 06:30 start at in the top willows at Billinge but I don't think I missed much as a result, at least I hope not. I set three 18m nets under clear blue skies and with only a light breeze blowing from the NE. The catching rate was better than expected for this early in the month and suggests it has been a fairly productive breeding season, especially when compared with the last couple of years. I packed up at 11:00 as the sun was shining on all the nets by then, making them much more visible, and before it got too hot.

The final total of 44 new birds and 2 retraps was mainly comprised of juveniles and included 32 warblers, 17 of which were Blackcaps. The two retraps were an adult male Blackcap that was originally ringed as a juvenile in July 2015 and a juvenile Blackcap that was ringed just over a week ago. The Blackcaps were mainly feeding on raspberries that grow wild near one of the net rides and most of them were caught in that particular net. This raspberry patch usually attracts and holds a good number of locally bred juveniles in July although 17 is more than I usually catch in one session.

Juvenile Blackcap

Juvenile Willow Tit.
Late June and July is the peak period for juvenile dispersal in this species and this is the 3rd to be ringed at the site in the last week.

Juvenile Treecreeper
July is also a time when the young of woodland species disperse and can be encountered well away from their usual habitat. 

There was some interest overhead with the highlight being a Crossbill that called loudly as it flew SW. A Siskin was also heard but not seen and a few Swallows seemed to be heading south. I wasn't in the best place to observe the Swallow movement but small groups appeared to motoring south from time to time; they certainly weren't the feeding flights of the local breeders.

Ringing totals for 12/07/17 (retraps in brackets) were: Blue Tit 2; Great Tit 2; Willow Tit 1; Goldcrest 1; Chiffchaff 5; Willow Warbler 10; Blackcap 15 (2); Treecreeper 1; Wren 1; Goldfinch 6.

Bilinge 9th July 2017 - more Swallows

I had planned an early morning ringing session in the top willows but I just couldn't motivate myself when the alarm went off, despite the weather conditions being near perfect. I decided some extra sleep was the order of the day; a decision that was made much easier because I knew I had the option of going up in the evening instead. I suppose I could, and perhaps should, have done both but I will save that kind of effort for later in the season.

I went to site at 7pm and quickly set 2 nets in the willows. I could hear a few warblers calling in the bushes as I was setting up but one thing that was absent was any sizeable tit flocks, not that I am complaining, although I did hear some Long-tailed Tits in the distance later on. There were quite few Swallows hawking insects overhead so I was hopeful that some would come into roost again and thankfully they did.

Part of the Swallow catch. I don't know why this site usually gets an early Swallow roost but it does, although numbers and duration of occupancy of the roost have varied from year to year. However, its future may be limited by the growth of the trees as the birds seem to prefer to roost in willows that average about 1.5 to 2 metres tall and some are more than twice that height now.

Juvenile Swallow

Adult male Swallow showing a fine pair of tail streamers.

The total of 41 new birds and 1 retrap was a good result with the majority of the catch being made up of Swallows and warblers. The individual totals (retraps in brackets) were: Blue Tit 1; Willow Tit 1; Swallow 23; Chiffchaff 4; Willow Warbler 3 (1); Blackcap 5; Blackbird 1; Goldfinch 2, Reed Bunting 1.

Observations of note were a Noctule Bat, surprisingly the first I have seen over the site, and as I was leaving I could hear a Grasshopper Warbler reeling from the territory in NE corner.

Billinge: 4th & 7th July 2017

4th July
This was a dual purpose evening visit to do a bit of ringing and work on clearing some of the summer's growth from one of the net rides in the top willows. I didn't get to site as early as I had originally planned so I only put up one 18m net rather than two as intended but that didn't matter as there was plenty of pruning to do.

The single net produced a trickle of birds which left me enough time to get another net ride cleared and ready for the rest of the autumn. As sunset approached I started to think about packing up but then some Swallows appeared so I stayed until they came into roost and I ended up catching 25 of them. The final ringing totals (retraps in brackets) were: Blue Tit 1; Swallow 25; Chiffchaff 2 (1); Willow Warbler 4 (2); Blackcap 2; Goldfinch 1. Total 35 new birds and 3 retraps.

7th July
I only got up after the 3rd alarm and some snoozing so not the early start that I had intended. I set 3 nets in the NE corner of the site and was set up by 06:40. Two Grasshopper Warblers were reeling nearby with one being in the same area as a bird recorded in early May but the other was singing in a less expected location and was reeling in the adjacent field of barley.

The catching rate was slow to start with but improved as the morning went on, although it didn't get busy. Highlights were 2 juvenile and an adult Grasshopper Warbler with the adult being a retrap male that was originally ringed on 2nd May this year. This strongly suggest they have bred successfully and constitutes the first breeding record for the site, although a bird held a territory last year and may have bred. The rest of the catch was fairly typical for this part of the site at this time of year and included the first juvenile Goldcrests and a juvenile Willow Tit.

Juvenile Grasshopper Warbler

Juvenile Grasshopper Warbler,

The two juvenile Grasshopper Warblers showed some of the variation in colour this species can display with one having mainly white underparts and the other having buff coloured underparts.

Juvenile Goldcrests always look scruffy as they go through their post-juvenile moult

This bird was just starting to show orange feathers (encased in sheath) growing in the crown which meant it could be sexed as a male. 

Juvenile Willow Tit.

Another feature of the site at this time of year are frequent encounters horse-flies and clegs and I donated far too much blood to their kind during the session. Luckily I haven't had any adverse reactions but these insects will continue to be a pain in the neck or other parts of the body during visits over the next few weeks.

There was a little bit of movement overhead with 1 Siskin heading south and 3 singles heading north and a Grey Wagtail heading south was particularly early for that species to be on the move.

Ringing totals for the 7th were: Goldcrest 2; Blue Tit 5; Great Tit 4; Coal Tit 1; Willow Tit 1; Chiffchaff 7; Willow Warbler 2; Blackcap 1; Grashopper Warbler 2 (1); Wren 1; Robin 1; Bullfinch (1). Total 27 new birds and 2 retraps.

Long time no blogging

Where did June go; it doesn't seem like the best part of a month has gone by since my last post but it has. I've not done much ringing this June compared to previous years but I haven't been idle either, far from it. I have had quite a lot of commitments over the last few weeks and I also decided to get stuck into some jobs around the house and garden and get them out of the way before autumn migration really gets going later this month. Having said that I still managed to ring 162 birds in June but 122 of those were Starlings in the garden.

It is fair to say this has been my best year for Starlings by some margin with 140 adults and 383 juveniles ringed in the garden up to the end of June. In addition there have been 436 resightings/recaptures involving 141 different individuals. Most of these resightings were of birds that were ringed or colour-ringed in previous years with the oldest individuals having been ringed as adults in 2011. The current longevity record for a Starling is 17 years, 7 months and 25 days so my project will have to run for a long time yet for me to see anything approaching that record, although reaching 6 or 7 years is still a very good age for a Starling.

I have been up to Billinge a few times recently to maintain the net rides in preparation for the autumn and I did put up a couple of nets on the evening of 26th June in two of the newly cleared rides. This short session produced 26 new birds and 1 retrap as follows - Willow Warbler 11, Chiffchaff 5 (1), Linnet 4, Great Tit 1, Blue Tit 1, Swallow 4. The 4 Swallows were interesting as they were all adult males that came in to roost in the willows. This site has held an early roost since I first started monitoring there in 2014 and a high proportion of adults has usually been a feature of the early catches.

That pretty much sums up how June went for me but now we are in July and autumn migration is starting to get underway there should be a lot more to blog about. With a bit of luck you should start to see a return to more regular updates from now on.