Crappy place to ring

Matt Prior writes:

You wouldn’t normally think of sewage treatment sites as wildlife havens but they are often sought out by bird ringers because they are indeed very attractive to birds. A particular treatment process, percolating filters, are rich with fly larvae, worms and snails that graze on the bacteria that treat the sewage. Sewage works are particularly beneficial to birds in the winter providing an insect food source during cold weather because the filters rarely freeze due to the warmth of the sewage. Accessing such sites is difficult and requires robust risk assessments and method statements and ringers have to take the unusual steps to wear full personal protective equipment including hard hats and high visibility clothing.


Sewage treatment works in the snow. Photo by Lee Barber

Grey Wagtails are present at most sewage works; ringing studies have shown that many breed and are resident. In the winter Grey Wagtail numbers increase, presumably from birds originating in upland areas and we have seen that with a bird ringed as a nestling in the Welsh mountains that was retrapped at Marlborough sewage works in the winter. In March, we ringed a Grey Wagtail at Marlborough sewage works and this bird was retrapped by a ringer in Belgium in June. This is the first example of a BTO ringed Grey Wagtail to be recovered in Belgium. We contacted the Belgian ringer and he recorded it as a male and thinks it was breeding nearby.

Some years ago, a Grey Wagtail was retrapped at Calne sewage works that was originally ringed in Denmark so ringing shows that our wintering Grey Wagtails come from the continent as well as from Britain or Ireland. In addition to mapping movements, bird ringing can provide information about survival and on 4 December 2016 we retrapped a Grey Wagtail that we originally ringed on 23 January 2010 making it 6 years 10 months 19 days old; just short of the BTO longevity record.


Grey Wagtail. Phone by Lee Barber

Sewage works are also very attractive to Pied Wagtails and Meadow Pipits. Meadow Pipits have shown some level of winter site fidelity at Marlborough sewage works with many retrapped in subsequent winters and some returning for up to five years but we haven’t yet learnt where they are breeding.

Pied Wagtail. Photo by Lee Barber

Chiffchaffs are another bird that are now strongly associated with sewage works. Thousands now winter across the UK and sewage works are definitely the most popular site for them. Birdwatchers seek out these sites to look for Chiffchaffs in the hope of finding a browner looking one that is Siberian Chiffchaff. If we retrap one originally ringed on its breeding grounds that really would be exciting. Personally I have not been that lucky but I have retrapped a Chiffchaff that had originally been ringed in Belgium. We will continue to monitor birds on sewage works and who knows what we will learn next.

We're stuck in 2016

Since the end of 2016, the Demography Team has been hard at work loading all the ringing data received from our ringers. Data are still coming in by the 'file load', but here is a sneak peek at a few highlights of 2016.

The big question is always, "how many birds were ringed in 2016?". I don't think we will reach a million birds ringed this year, possibly due to Blue and Great Tit not having a great year. We are currently on 990,808 birds ringed and there is a corresponding 281,880 records of birds already wearing rings (either caught again by ringers or found dead by anyone).

The graph below shows the 20 most ringed species in 2016. Despite them having a poor year, Blue Tit is still by far the most ringed species but perhaps more interestingly, Goldfinch is in second place. BirdTrends records show that Goldfinch numbers have increased substantially in recent years; however it is only the 10th most recaught species.




Top 20 species of birds ringed in 2016. Click to enlarge.

Unlike Willow Warbler, Chiffchaff has been doing very well recently, and as you can see from the graph, was the fourth most ringed bird in 2016. The preliminary results from the CES scheme show that Chiffchaff had the highest adult abundance in the history of the scheme last year. Unfortunately, productivity was significantly down in 2016 and the Nest Record Scheme results show that the mean laying date was eight days later than average. Chiffchaff that had originally been ringed in the Channel Islands, Germany, Spain, France, The Netherlands and Portugal were found in Britain and Ireland in 2016. All, apart from three birds were caught by our BTO ringers, one was found dead and two hit a window (one survived and one didn't).



A young Chiffchaff. Photo taken by Lee Barber

Coming in at number five of the most ringed bird for 2016 was Blackcap. This bird also had a high adult abundance and an even lower productivity than Chiffchaff  in the preliminary CES results. The North Wilts RG ringed an impressive 2,209 Blackcap in 2016, and their ringing session on 11 September, where they caught 257 Blackcap (most of which would have been on autumn passage), will always be remembered by the team on that day.

Male Blackcap. Photo taken by John Dunn.

Some of the more unusual recoveries we received in 2016 include a Blackcap which was found in a 'Horse water bucket', ringed by the West Wilts RG in 2011. We occasionally get birds being hit by vehicles, however I have never heard before of one which was 'trapped inside locked vehicle (entered through partly open window), fresh dead'. We also received a report of the fourth Slovenian ringed Blackcap found by a non-ringer. There are still a few records to be processed of BTO-ringed Blackcap that were found abroad and we look forward to processing those and letting the ringers know if it is one of theirs.

All of the recoveries of fresh dead birds and recaptures of live birds, feed into the longevity records for Britain and Ireland. It will be a little while until the 2016 records are added, but there are a couple of records that look to update the current longevities. The Bisham Barn Owl Group look to have just pipped the current record by a few days, originally set in 2012 (of 15 years 3 months). Click here for more information. The Mediterranean Gull record currently stand at 15 years 3 months as well, and Allan Hale has reported two colour ringed Med Gulls at Great Yarmouth beach, which were ringed just two days apart breaking the current record by over three months.

This post covers just covers the tip of a very big 'data' iceburg, so as we have more time to look into this data, we will undoubtably uncover more exciting information.

Chiff-ful start to the nesting season

Over in Cambridgeshire there’s been wonderful sunshine, but accompanied by overnight frosts. Thankfully this hasn’t put off the resident birds at the National Trust’s Wicken Fen National Nature Reserve, where members of the ringing and nest recording group are getting ready to ring the first broods of Blackbirds. Also, our first Coot brood has just hatched, Long-tailed Tit clutches are about to hatch, Blue Tits and Great Tits are laying, and we’ve started monitoring our first finch nests: an almost fully-built Chaffinch nest was found a week ago and a pair of Goldfinches were spotted building last Thursday.

Water birds such as Coot (pictured) and Moorhen commonly hatch their first broods in mid-April

As for summer migrants, arrivals have been stalled by strong north-westerly winds, according to the BTO migration blog, and indeed Blackcaps at Wicken have been singing on territory for only a week and Willow Warblers still seem thin on the ground. One short-distance migrant, though, has been getting off to a flying start this season and keeping our nest finders very busy: Chiffchaff!

During Easter weekend we saw plenty of male Chiffchaffs singing from tree tops but no birds skulking lower down (a tell-tale sign of a female getting ready to build). Last Monday, things had got busier: males were singing back-to-back and chasing each other off territories and ‘hueet’ contact calls could be heard everywhere. Then, on Tuesday 14, we caught our first glimpse of a bird with a beakful of long grass—a building female! Early next morning we spotted another bird building and then on Thursday 16, Anne, our main nest finder, found five more nests, some almost fully formed (a characteristic domed construction). By Monday 20, we had found 11 nests, two lined with feathers, and that morning we found nest number 12 at an early stage, the female pinging back-and-forth with large bits of material.

Chiffchaff nest at Wicken Fen in 2014. Built just above the ground, the nest is dome shaped, made from reeds and some finer grasses, and lined with feathers. c.200 Chiffchaff nests are monitored across the country for NRS each year.

So what to expect this weekend? Those lined nests will probably have eggs, though females may still be building on other territories. Nest recorders elsewhere have begun reporting Blackcaps on eggs, Whitethroats and Willow Warblers building, and Chaffinches on full clutches.

How far along are nesting birds on your patch? Help the BTO collect vital data on nest productivity and timing of breeding by taking part in the Nest Record Scheme.

Unusual Winter Warblers?

During these cold winter days it is nice to think back to the summer full of the song of the Whitethroat, Willow Warbler and the reeling Grasshopper Warbler. Whilst most warblers migrate from Britain & Ireland to enjoy the warmth of their African wintering grounds, some migrate from Europe to spend the winter here. Blackcaps have been commented on before, here, here, and here, but they are not the only warbler species seen here in winter.

There are usually quite a few Blackcaps and Chiffchaffs seen in the country at this time of year, with the odd Yellow-browed Warbler present in the south. However, last Friday (30/01/2014) a Reed Warbler was caught at Chew Valley Ringing Station, North Somerset! This bird should have been in Sub-Saharan Africa at this time of year. There is one previous electronic record of a Reed Warbler being ringed in January (a bird ringed in Hertfordshire in 1981) whilst there are two records of birds ringed in December (2000 and 2003).

The graph below shows the average number of ringed Reed Warbler, Chiffchaff and Blackcap over the last five years. Reed Warbler just makes an appearance in November but is swamped by the over wintering Chiffchaff and Blackcap. Birdtrack data show a similar pattern in the seasonal abundance of these wintering warblers.

There are many parameters that govern the over-winter survival of these birds and there are clear differences between years. Temperature can greatly affect food resources, especially for insectivorous species. The graph below shows the number of Chiffchaff ringed in winter and you can see the figure for the winter of 2010/2011 (which was very cold) drops substantially.

Numbers ringed during November appear to have increased recently, but this is not reflected in late winter catches. This suggests that more birds are arriving in the UK, but either dying, moving on southwards or dispersing into areas away from ringing hotspots like sewage works that are already at carrying capacity. More systematic winter ringing across a wider range of sites is required to identify which of these mechanisms is responsible.

Spring encounters of the bird kind

You will be glad to hear that we are now reaching the 'tail end' of the auk wreck that has effected thousands of Puffins, Guillemots and Razorbills up and down the country (posted previously). We are still however receiving reports from the various ringing schemes involved, showing the great distances these birds can travel during the winter.

Collared Doves have been known to make large movements occasionally and one such bird travelled south from Fair Isle, Shetland all the way to Halkirk, Caithness (238km) to end up being killed by a cat on the 06 April. Reports of interesting movements of Chaffinch include two Norwegian ringed birds, one killed by a cat in Powys and one to be found fresh dead in Wiltshire both found in mid March. At a very similar time a BTO ringed Chaffinch from Lincolnshire met his end in Norway after not seeing a window in time.

Chaffinch - John Harding

Windows were also responsible for 2 BTO ringed Dunnock recoveries of note. One was the 11th record to Norway (again ringed in Lincolnshire - 1721km) and the other was the 2nd ever Dunnock to be found in Denmark (ringed in Suffolk - 744km).

The BTO migration blog and BirdTrack is currently showing a good influx of spring migrants at the moment with species like Chiffchaff, Blackcap and Swallow, and with this comes encounters with ringed migrants. A Sussex ringed Chiffchaff for example (ringed in September 2013) met its end on its return migration when it was found dead in someone's kitchen in Spain (928km).

BirdTrack reporting rate of Chiffchaff

We have also received our first report of a returning Osprey, to the Glaslyn Osprey Centre near Porthmadog, Gwynedd. This bird was identified by a video camera placed near the nest during the winter. It was originally ringed as a chick at Rutland Water in 1998 in a brood of three.

A window was the likely cause of a Lincolnshire ringed Oystercatcher death in Norway (733km) but more positively, several Irish ringed Oystercatchers have been seen in their breeding grounds in Iceland (1519km).

First BTO Chiffchaff to Hungary

It's not every day we see recoveries of passerines in Hungary, as it's much more expected to see records of things like colour-ringed Mediterranean Gulls from there (almost 1000 to date!). In fact, there are just two records of BTO-ringed passerines found in Hungary and, unsurprisingly, both were Lesser Whitethroats. The other way round, the only Hungarian-ringed passerine found here was the equally exceptional record of a Sand Martin recaught by ringers in Lincolnshire in 2008.

So it was a pleasant surprise to hear of a BTO-ringed Chiffchaff caught in Hungary (at Hódmezővásárhely, Csongrád) on 2nd November, shown by the star on the map below. This bird had been ringed as a juvenile at Eskmeals, Cumbria, in July 2013, so was presumably still on southward migration when recaught: or perhaps displaced by the back end of 'St Jude'?

ADV129 when recaught recently in Hungary

Foreign finding and ringing locations of UK Chiffchaffs

It would seem more likely to find a British Chiffchaff so far east on spring migration, but oddly the only vaguely similar record concerns a Ukrainian-ringed bird killed by a cat in Peterhead, Grampian, in December 1987. This bird had been ringed two months earlier so who knows where it was going!

Thanks (and congratulations) to Erna Borbáth for the photos of the bird in Hungary.

It's all about the sewage

It’s well known that wintering Chiffchaffs have a great affinity with the southwest, with Devon and Cornwall home to an unknown, but undoubtedly large, proportion of the UK wintering population. Looking back at just the last five winters (December to February in each of 2006-07 to 2010-11), we hold electronic ringing records of 918 Chiffchaffs, with no fewer than 244 ringed in Devon and 187 in Cornwall. Over these years, the highest winter total was 86 birds ringed in Devon in 2008-09.

Despite this winter being relatively mild, we’ve been having great success in catching wintering Chiffchaffs at several sites in Cornwall, thanks largely to the support of South West Water in allowing us access to works areas. Since the start of the year, we’ve ringed 105 Chiffchaffs at just three sewage works in Cornwall, including 41 on one day alone. This compares well to previous years, with the highest winter total nationally being 265 in 2009-10.



The racial identity of these birds is also interesting, with a small proportion being of northern races: either abietinus or tristis (Siberian Chiffchaff, above). Interestingly though, yesterday morning saw us catch a French-ringed bird, perhaps indicating an alternative origin of these wintering birds. There are just 13 previous records of French-ringed Chiffchaffs in the UK, of which three have been in Cornwall and two in Devon.

The sewage works sites are also important for various other wintering species, and yesterday’s catch also included two Firecrests and two Yellow-browed Warblers (below) in amongst the more expected 35 Chiffchaffs. The Yellow-broweds are of particular note, as of the 902 electronic ringing records we hold, just six have been in winter (five in December and one in January).



Thanks to Ashley Hugo for the tristis Chiff photo and Adam Hartley for the Yellow-broweds.

October oddities and November notables

Grampian Ringing Group definitely got the distance prize for October with a Sandwich Tern turning up in Liberia, West Africa (5679km in 488 days). This chick was ringed at Sands of Forvie Nature Reserve, Aberdeenshire last year and was caught by children playing on the beach in Robertsport but unfortunately died.

We also received 8 reports of Lesser Black-backed Gull wintering in Portugal and all but one were live sightings. Mute Swans were also very evident with lots of sightings but some hitting overhead power cables and one or two in poor condition. Unusually we didn't get many reports of Barn Owls in poor condition but we did get 12 reports of car victims. All of the ones that died were ringed as chicks this year. One bird, strangely, was seen flying straight into a wall and then a parked car before being rescued and taken into care.


There was also a nice Blackcap report "found and released" on 25th October in Tizi-Ouzou, Algiers, Algeria that was ringed near Sleaford, Lincolnshire in May this year (1839km in 174 days). Another notable passerine was a Chiffchaff ringed in Northumberland in August and was found dead after connecting with a vehicle in Candresse, France in October (1257km in 37 days!)

All the above recoveries have been processed and found in either October or November. We are still getting reports of birds found in November so this is not an exhaustive list. Thanks to Dawn Balmer for the photo.

Migrant Misfortunes in April

With the mass exodus of the winter migrants just about over and with most of 'our' birds settling down to breed, its time to look forward to all the summer migrant recoveries. This afternoon Dave Leech was ecstatic with his discovery of 2 Blackcap nests and we have also been receiving a few recoveries of this species as well. This includes a Blackcap ringed at South Foreland, Kent on 2nd Oct 2010 which was caught by a ringer at Litcham, Norfolk 11 Apr 2011 (181km in 191 days).

Chiffchaff have been doing well for reports, with 7 birds so far this month, 4 of which died when they hit windows. Another was very unlucky when it was hit by a car at Great Bowden, Leicestershire on 20 Apr 2011, after being ringed at Abbotsbury Swannery, Dorset in October 2010 (236km in 200 days).


We received a report through www.ring.ac on 17th April concerning an unidentified bird being found freshly dead at Skipness, Knapdale. This turned out to be a recently returned Manx Shearwater which was ringed at Copeland Bird Observatory, Co Down in 2003. The distance between these two sites is 120km but this bird travelled considerably more, since they winter off the coast of Argentina every year.

A look at some other reports of interest reveals a rarely ringed Ring-necked Parakeet which was found on the M4 after being hit by a vehicle, also found on the 17th April. This bird was ringed 10km away at Molesey Lock, Surrey. There is also a cracking recovery (although unfortunate for the bird) of a Pochard (red pin below), being shot in Bezenchuk, Samara in Russia (3290km in 486 days). A Woodcock (blue pin below) was also shot but this time in Belarus after being ringed in 2006 at Stowmarket, Suffolk (1830km in 1568 days).


View Pochard and Woodcock Recoveries in a larger map

Note these are recent reports and haven't yet gone through the checking process.
Thanks to Dawn Balmer for the Chiffchaff picture.

Colder temperatures bring in the birds

Every week we receive reports from Ringing Schemes all over Europe and today we have received a batch of records from Stavanger (Norway).

This included 2 Norwegian ringed Robins, both caught by UK ringers, one at Kilnsea, East Yorkshire (ringed 170 days before in Rogaland, Norway) and the other at Hartlepool, Cleveland (ringed 18 days before in Buskerud, Norway).


With this cold weather Brambling should be quite settled in the UK now and one such bird was controlled at Spurn Point, East Yorkshire which was ringed in Sept 2009 in Rogaland. On the other end of the seasonal scale a Chiffchaff was controlled also at Kilnsea, East Yorkshire which turns out to be the 8th from Norway! It was ringed 69 days before (23.7.2010) at Grimstadvatnet, Hareid, More og Romsdal.


View Chiffchaff from Norway in a larger map

And finally a Kestrel was reported freshly dead and very thin at Swanley, Kent on 19th Sept 2010 which had been ringed as a chick on 30 June 2010, 1326km away at Galasflota Nord, Hedmark, Norway.

Thanks to Stavanger and Dawn Balmer for the photo.