Out of Africa... and into Norfolk, for a 13 gram bird

Oliver Fox writes:

Monitoring of wintering passerines is one of the main objectives of the Kartong Bird Observatory (KBO), a project run by volunteer ringers in the south of The Gambia, West Africa. Situated on the Atlantic coast close to the Senegalese border, the Kartong wetlands were formed relatively recently as a result of wet-season flooding of disused sand mines and form part of the Allahein to Kartong coast IBA.


Palearctic passerines being processed at Kartong Bird Observatory taken by Colin cross



The wetland reedbeds and surrounding scrub provides an excellent wintering site for many Palearctic passerines, and mist-net surveys have highlighted the importance of the site for Western Olivaceous Warblers, Common Whitethroats, Subalpine Warblers and Common Nightingales in particular. In dry years the area provides refuge for Sahel-dependent species, such as Western Orphean Warblers and Woodchat Shrikes, when conditions further north become unfavourable. Located on a promontory extending into the Atlantic, the site is also well placed to observe passage migration of Blackcaps and Garden Warblers moving south in October and November and Willow Warblers moving north in early Spring.

Wintering Reed Warblers are regularly encountered at Kartong, both in the Typhus reedbeds and the dry coastal and Acacia scrub that surrounds the wetlands. A proportion of those ringed at Kartong seem to be faithful to the wintering site, with five birds recaptured the winter after ringing and one bird returning to Kartong in two successive winters.

Reed Warbler about to be released at Kartong taken by Oliver Fox

News from the BTO has been received that a Reed Warbler ringed on 18/01/14 at Kartong was recaught at Hilgay Wetland Creation, Norfolk on 11/08/2015 BTO's Graham Austin, only 29 km from BTO HQ. There were several BTO staff members on the expedition in 2014, so it seems fitting that the bird was caught in Norfolk a few months later.

This is the sixth Reed Warbler ringed at KBO to be recaptured back in Europe during the summer months, with three having been previously recaptured in Spain, one on Guernsey and one in Surrey. Similarly, the ringing teams at Kartong have recaptured two Spanish and one British & Irish-ringed bird in the last few years, showing the migration pattern of Reed Warblers from Western Europe to the coast of West Africa.

Details of this latest recovery can be found on the Recoveries and Controls page of the KBO website.

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.

Nice weather for nesting

Having put up with dampened breeding success in 2012 and a chilled start to the season in 2013, how are breeding birds faring this year following the relatively fine winter and spring? This timely question from BBC Springwatch prompted the Demog team to appeal to BTO nest recorders and ringers for any mid-season information they could pull together. True to form, an amazing 112 responses were received from recorders in just two days, which we've summarised below for seven representative species.

Barn Owl

Last breeding season was a very poor one for Barn Owl because of the adverse spring weather and lack of voles. Many birds did not even attempt to nest. Preliminary reports for 2014 from the nine recorders who contacted us about Barn Owl are much more positive, however: high site occupancy rates, laying 2-3 weeks ahead of schedule in places, large clutch sizes and large broods. There has also been some exceptionally early laying: Peter Rose in Northumberland found a Barn Owl pair on eggs in late February. This season's promising start has no doubt been aided by mild conditions but, as Colin Shawyer anticipated in his forecast for the season, the most important feature has been the incredibly high vole numbers, confirmed by the large food caches being reported in boxes.

A Barn Owl box with young looking out. Barn Owl box occupancy rates are reported to be back up this year after many birds didn't breed in 2013. Photo by Dave Short

Kestrel

Reports form BTO nest recorders in Lancashire, Cheshire and Lincolnshire suggest that laying is 1-2 weeks earlier than average in 2014 and up to three weeks earlier than last year. As with Barn Owls, this may reflect a plentiful food supply in addition to the warm temperatures. Clutch and brood sizes seem to be above average, again due to the large amount of mammalian prey. The reported early start will give young more time to build up strength and learn to hunt before winter, which may increase survival.

A brood of five Kestrel chicks in a box inspected by Essex nest recorder Steve Baines last week. Photo by Steve Baines

Peregrine

Reports from nest recorders in southwest England and Shropshire suggest that laying dates are not significantly different from the average. In contrast to the vole-dependent raptors like Kestrel and Barn Owl, Peregrines seem to be having an average to poor year in terms of numbers of breeding pairs and brood sizes. The wet weather in late spring may have reduced female condition, resulting in suspension of breeding and/or small clutches. Wet summers can adversely affect Peregrines by reducing prey activity levels and therefore hunting efficiency.

Swallow

Reports from 25 recorders suggest that laying is occurring a week or so earlier than last year, which is similar timing to previous warm years, such as 2011, and within typical levels of annual variation. As with Reed Warblers, the odd early attempt was noted: John Lloyd in Carmarthernshire recorded his first April eggs in 40 years of monitoring. A reasonably early start bodes well for repeat broods this year, so long as there isn't prolonged heavy rain, which can prevent birds hunting for airbourne insects. Large clutch sizes have also been reported this season.

Reed Warbler

This long-distance migrant rarely gets going before May - there are only 11 Reed Warbler nest records with April laying dates out of an NRS dataset of 10,000 - but this season several nests with eggs in April have been monitored by recorders in south Wales, Avon and Norfolk. However, it appears that these few early nesting attempts, enabled by warm weather stimulating good, early reed growth, were followed by a delay of 1-2 weeks before the main body of birds began laying at the normal time. This may have been due to delays on passage caused by cold, wet weather in southern France and Spain. BirdTrack data show that the timing of arrival in the UK was similar to recent years, from the second week of April onwards.

The peak breeding period for Reed Warbler, a long-distance migrant, begins in mid-May and finishes at the end of July. A pair will have 1-2 broods a year. Photo by John Harding

Blue Tit

Last season was one of the latest for nesting Blue Tit since the mid-1960s. From early reports this season, however, it appears this is one of the earliest on record, with laying 2-3 weeks earlier than normal. Andy Turner in Oxfordshire recorded a mean first egg date of 9th April, almost a month earlier than 2013 (6th May). Clutch sizes appear to have been average to below average - this could be down to high adult abundance, and therefore competition, following the good survival prospects over the 2013/14 warm winter. However, warmer springs also tend to be poor for productivity as, although birds advance their laying, caterpillars advance emergence by a greater amount, therefore reducing the synchrony between demand from chicks and availability of insect food. Moreover, the recent wet weather appears to have had a negative impact on chick survival - wet summers in general are problematic as they wash much of the insect food from the canopy.

Long-tailed Tit

Despite the warm weather in February and March, reported laying dates this season are close to the average, if towards the early end, with most clutches being built between late March and mid April. The wet weather in late winter may have delayed breeding somewhat if it meant that females struggled to find food and began the season in poor condition. Preliminary reports from ringers suggest that numbers of fledglings are much higher this season compared to 2013, which was particularly poor for Long-tailed Tit, owing to the very low temperatures in late winter and early spring. Warm, dry weather benefits fledgling survival as small birds can chill easily when wet.

Long-tailed Tit is one of our earliest breeders, typically laying from late March until early May. They only have one brood per year, although may relay if the first fails. Photo by Elspeth Rowe

Many thanks indeed to

Alan Ball, Bob Sheppard & Keith Bowden, James Anderson, Steve Baines, Tim Ball, Batty and Bateman, Phil Belman, BIAZA Nest Recording Project, Derek & Mary Bickerton, Rorger Bird, Bristol Naturalists Society, Paul Cammack, Steve Carter, Barry Caudwell, Centre for Ecology and Hydrology, Charnwood Ringing Group, Michael Colquhoun, Brenda Cook, Simon Cox, Ruth Croger, Crombie Country Park, Cwm Clydach RSPB Reserve, Robert Danson, Chris Dee, Richard Denyer, Derek Holman, Karl Ivens and Andy Glover, Thomas Dewdney, Ed Drewitt, David Dutton, East Dales Ringing Group, Chris Evans, Mark Fletcher, Jeremy Gates, Adrian George, Steve Gray, Philip Hanmer, David Harazny, Ian Hartley, John High, Kenneth Hindmarch, Peter Holmes, Mike Hounsome, Michael Hunt, Cynthia Hyde, Iain Inglis, Peter Johnson, Kelvin Jones, Tom Kittle, Lancaster & District Birdwatching Society, John Lawton Roberts, Alan Levitt, Jerry Lewis, John Lloyd, Garth Lowe, John Mark, Frank Mawby, Philip May, Kevin May, Michael McDowall, David Mckee, Merseyside Ringing Group, Minsmere RSPB Reserve, Colin Moody, Gerald Murphy, Mervyn Needham, Ian Nicholson, North Cotswold OS, North-west Norfolk Ringing Group, NT Farne Islands, Parc Natur Penglais Support Group, Keith Parkes, Pinley Abbey Nature Reserve, Pitsford Reservoir, Andrew Ramsay, Derek Robertson, Paul Robinson, Peter Rose, Paul Roughley, RSPB Fowlmere, RSPB Grange Farm, Salisbury Plain MOD Conservation Group, Malcolm Samuels, Robin Scott, Keith Seaton, Dave Short, Shropshire Peregrine Group, Doug Simpson, Judith Smith, Sorby Breck Ringing Group, South Derbyshire (Souder) Ringing Group, South Devon Nestbox Group, South East Cheshire Ornithological Society, South West Lancashire Ringing Group, South West Peregrine Group, Derek Spooner, Ian Standivan, Suffolk Community Barn Owl Project, Tay Ringing Group, Simon Taylor, Roger Taylor, John Thompson, Treswell Wood IPM Group, Andy Turner, Stephanie Tyler, David Warden, Barrie Watson, Waveney Ringing Group, Denise Wawman, West Midland Bird Club, West Midland Bird Club Boddenham, Williams and Tabor, Wirral Barn Owl Trust, Ian Wrisdale

Waiting for the kids to leave home

Over 36,000 Reed Warblers were ringed in the UK during 2010, so what was interesting about the seven caught at a site in south Norfolk on Thursday?

During the summer of 2011, a team of BTO staff, collectively known as The Swamp Things (AKA Dave Leech, Lee Barber, Rachael Portnall, Mike Toms and Jez Blackburn), decided that the best way to spend their free time would be to slip into a pair chest waders and wander the reedbeds of Norfolk. Why, you ask? A good question, especially when the temperature rises into the high twenties and the horseflies are hungry, but there was method in their madness as there really is no other way to collect data on the nesting success of Reed Warblers.

So, when the warblers arrived back from Africa in April, The Swamp Things sprang into action, catching and ringing the adults, finding their nests and ringing the chicks. The first full clutch of eggs was recorded on the 8th May, and the last nestling was ringed on the 12th August, by which time several of the team were looking considerably sleeker and, at least from the shoulders up, more tanned. In the intervening three months, they monitored 257 nests and ringed 596 nestlings. An added bonus was provided by the 12 nests parasitized by Cuckoos, of which at least seven were thought to have fledged (and by now have presumably joined Clement , Martin, Caspar, Lyster, and Chris on their wintering grounds).

The seven birds mentioned at the top of this posting were all ringed as chicks in the nest between the 8th and the 30th July and are still finishing their moult and building up their fat reserves. By adding this information to the other recaptures of ringed nestlings, the team will be able to learn a lot more about the behaviour of the youngsters when they reach independence and prepare for their first ever migration, an incredibly important, yet seldom studied, period in their lives.

Thanks to Dave Leech for this post.

Ringing Course at Chew

I have just been on the Chew Valley Ringing Course in Somerset. This long standing course offered training in mist netting of various species covering Reed habitat, garden birds and also hirundines. Together with this information on moult stratagies and other catching methods were also given.

This year there were mainly trainee ringers attending the course and we had a good mix of birds caught and we were able to look at their plumage in great detail. This is a regular ringing site so there were plenty of known age birds. About 300 birds were caught during the 3 days including a bird that was ringed further north by West Wiltshire Ringing Group and also an adult Sedge Warbler that was already ringed by the French Ringing Scheme (Paris)! Ringing details are on there way.

Ringing Courses are an excellent way for ringers to get extra experience in various aspects of ringing and also be assessed for permit upgrades. These are particularly useful for ringers applying for training endorsements. Courses are currently full for this year and usually run from June to October but future courses will be on the BTO website next year. It is advisable to book early!

Thanks to all that participated on the course and to Ed Drewitt for the photos and Mike Bailey for the image of the Paris ring.

Interesting Reed Warbler distribution

During their free time, a few BTO staff have been working hard, finding all the Reed Warbler nests on a large site near Mundford, Norfolk. This work also involves Constant Effort ringing and monitoring.

This encouraged us to think of where Reed Warblers are caught and originate from. Below is a map of Reed Warblers which were ringed in Britain and then recaught/found in 2010. You can clearly see the southward migration route and also the lack of birds in Northern Scotland.

The map is interactive so you can zoom in and out for more or less detail.

View Reed Warbler distribution in a full screen map

So where do birds from other countries, that are recaptured/found in Britain in 2010 come from? See below.

View Reed Warbler originating distribution in a full screen map

A good breeding season?

It is a wee bit early for any definitive results relating to this year's breeding season, but we always love to hear about good news stories. Earlier this week we heard from Rye Bay Ringing Group about their captures for July. Even by Rye Bay’s standards, their captures so far this year, for species such as Reed Warbler and Grasshopper Warbler, are quite spectacular (see the graphs below).


Similarly, according to CES ringers Ian Dillon and Alan Bull, the story from Paxton Pits in Cambridgeshire shows that migrants appear to have had a better season than residents. Has last winter’s cold winter had a big effect on this? Future CES results will shed light on this...

Reed Warbler bonanza

This year BTO staff (Dave Leech, Mike Toms, Jez Blackburn and myself) have made a big push to record Reed Warbler nesting attempts on the BTO Nunnery reserve and also at an old sand quarry nearby. We're attempting to find the majority of nests at each site, a challenging task given the depth of the water and the prolific output of the birds, many of which raise two broods per season. All the chicks are ringed, so we should be able to identify those who return from Africa to breed next year, and the adults are also being colour ringed in the hope that we can identify which birds are responsible for producing which youngsters.


Over 130 nests have been found since the start of June and around 150 chicks ringed, together with three Cuckoo chicks that had evicted the previous tennants. One of the Reed Warblers (X465599) has already been caught by ringer John Walshe at Lackford, Suffolk, having travelled 16km to a completely different reedbed within a month of leaving the nest. Did it make the journey on its own or with siblings, and are movements to other sites soon after fledging a regular occurence? These are the sort of quesitons that we hope to be able to answer in the longer term.

Thanks to John Walshe and Dave Leech for the photo.

Merry Christmas bloggers!

Just as we're in the midst of one of a big freeze, some birds just seem to be ignoring it completely. This week we had a report of a Canada Goose sitting on five eggs on a canal right in the middle of Manchester (not quite the one below), so it'll be interesting to see how it fares.



We've also hear of a Robin apparently nest-building in late November (Suffolk), a female Mallard with 14 day-old ducklings in mid November (on a golf course pond in Hainault Forest, London) and also a late Reed Warbler caught in Sussex on 1 December (it was originally ringed at the same site in late October).

If you find any odd nesting behaviour over the winter then we'd be interested to hear about it. All of us in the BTO Demography Team wish you a Merry Christmas and hope you have a New Year full of ringed birds and recorded nests!

Thanks to Judith Smith (Greater Manchester Bird Recorder) for letting us know about this bird.