Saturday, 31 August 2013

An influx of reedbed warblers ............

A pleasant morning with Keith Vaughton and Cedwyn Davies during which we caught a total of 58 birds at Oxwich Marsh.

The day started damp and cool, but the north-westerly wind remained light until mid morning, and the sun came out by around 07:00.

The catch was made up of: reed warbler (19), sedge warbler (8), chiffchaff (7), willow warbler (2), blackcap (1), reed bunting (1), blue tit (11), bullfinch (3), wren (3), robin (2) and treecreeper (1).  Therefore a nice mix of migrant warblers and resident species.

The catch of migrant warblers was dominated by juvenile birds, and there was no evidence (from fat deposits) that these were ready to make a long distance movement.  However, the sedge warbler, pictured to the left and below, was an adult and carrying significant fat.  This can be seen in the picture to the left.  The tracheal pit is full (in fact slightly convex and overlapping the breast muscle by several mm).  Fat is assessed using standard scoring system, and can be used to help understand the timing of migratory movements.  The feathers are gently blown to expose the skin. A more typical (!) photo of the sedge warbler is to the right.

Owain Gabb 31/08/2013

Sunday, 25 August 2013

Low numbers, but reasonable diversity

A light northerly wind, which gradually strengthened over the session and little cloud cover probably contributed to the catch in the Oxwich reedbed dropping off rapidly.  Despite 16 birds in the first net round, only 18 were caught in total, and we packed up just after 10am.

The 18 birds were made up of 3 wrens, 1 sedge warbler, a robin, a reed bunting, 3 reed warblers, 2 bullfinches, a Cetti's warbler, 2 blackcaps, a long-tailed tit, a blackbird, a blue tit and a kingfisher.

The highlight of the catch was the kingfisher. Photos are below.

The photo above shows the blue back and rump, the colouration of the head (blue-green), and the condition of the wing feathers (fresh).  In the photo below the brown colouration of the feet and grey fringes to the breast feathers can be seen.  This combination of features indicates a juvenile male.   

Other wildlife noted around or over the marsh included a fly over little egret, two sparrowhawks circling and chasing above the Penrice Estate, and the micro moth Acleris emargana (below).

Many thanks to Keith Vaughton for assistance and company.
Owain Gabb, 25/08/2013

Friday, 23 August 2013


Last night we decided to spend a few hours in pursuit of Nightjars on “Sarn Helen” a former Roman road connecting Nidum (Neath) with Segontium (Caernarfon). These nocturnal or crepuscular birds with bristles around their mouths (to perhaps assist them in the capture of insects whilst in flight) are an endangered species and their conservation status has been given a Red Alert. The Nightjar season is from May to September spending the rest of the year in Africa so we really had left our visit very late in the season to try and catch these elusive birds..

Anyway we had two 60ft nets set up and ready to go for about 8.30pm. The nets were about 150metres apart and as it got dark it wasn’t long before the trill of the male bird could be heard as he flew around our heads. Not long later it flew into the net. Just as the male had been processed the female also flew into the net. Since in a square kilometer there is probably only one mating pair we decided it was probably wise to pack up rather than risk catching the same birds a second time.

The bird above is the female. The male bird has white tips to its outer tail feathers.
Head shot of the male.

Thursday, 22 August 2013

Kenfig NNR 27 - 3 WWT Llanelli

Heather Coats and I joined Chris Newberry at Kenfig hoping for more success on CES 11 than we had at WWT's CES the previous Monday.
The weather was set fair with the promise of sunshine later in the morning.
Once again an additional 30 metres of net in the scrub was added to the 108 metres of net in the CES ride.
The total for the session was twenty seven with only two adults among them.
Species count was Whitethroat 7, Blue Tit 2, Blackcap 1, Sedge Warbler 2, Reed Warbler 10, Chiffchaff 1, Robin 1, Reed Bunting 1, Goldfinch 1, Cetti's Warbler 1.
This session made up for the (2 Wren and 1 Blackcap) we caught in our six-hour visit to Llanelli.

Juvenile Whitethroat

Wednesday, 21 August 2013

Crymlyn Bog

The last time we visited Crymlyn  Bog was early spring. Since then we have been actively involved with our CES sites. Crymlyn Bog managed by CCW is the largest lowland Fen in Wales. The nature reserve is surrounded by an industrial and residential landscape on the eastern edge of Swansea and was formed during the ice age.

Heather. Cedwyn and I met up at 05.30am this morning to set up 2 x 120ft net runs on the footpath that runs through the reed beds in the hope to catch some warblers before they start there Autumn migration. It was quite cool first thing and there was only the odd bird moving around. As it warmed plenty of Swallows started flying about many of which came low within feet of the ground and we thought it maybe possible to do a Swallow roost later in the month. But at this time we had not had a single bird in the nets, so at 08.45 we decided to call it a day and go home. As we approached the nets there were 4 birds in them1 x Sedge Warbler, 2 x Reed Warbler and a Wren. The Warblers showed no sign of fat deposits in preparation for migration, which was a surprise. 

The next visit produced a 1 x Robin, 1 x Reed Warbler and a Meadow Pipit which was in primary and body moult and it was interesting to note the secondary’s had started as well.

Saturday, 10 August 2013

Reed warblers in the ascendancy .....

A very light south-westerly wind and early cloud at Oxwich presented ideal conditions for ringing during the hour after dawn, but as the sun broke through catches per round steadily declined.  The nets were taken down at 09:45. 
The total catch was 25 birds: 10 reed warblers, 3 whitethroats, 3 blackcaps, 2 willow warblers, 2 dunnocks, 2 blue tits, and single Cetti's warbler, sedge warbler and wren.  Frustration was provided by a garden warbler, which managed to escape from a net prior to extraction, and which would otherwise have been the first trapped at the site in 2013.  Garden warbler is not a common breeding species on Gower.

The photographs below show a young whitethroat on the left and a reed warbler on the right.

A drop off in sedge warbler numbers was apparent in comparison with recent visits.  The only sedge warbler caught was an adult which was carrying significant fat (fat score of 6).    This indicated it was either preparing to migrate or had stopped in the reedbed before continuing its passage south.

Many juvenile birds are now approaching the end of or have finished their post juvenile moult.  These included the whitethroats, willow warblers and a few reed warblers.  However, some resident species have more than one brood, and one of the dunnocks and one of the wrens caught today were in entirely juvenile plumage, with un-feathered bellies and disseminated body feathering.
Invertebrates around the ringing station included wall brown, common blue and small copper butterflies, silver Y (moths), a female southern hawker and marsh horsefly.  A common lizard was seen basking on some roofing felt nearby.

Thanks to Keith Vaughton and Cerian Thomas for assistance and another good session.

Owain Gabb

Thursday, 8 August 2013

CES 10 at Kenfig NNR

Chris Newberry, Heather Coats and I once again met for a CES session at Kenfig.  We supplemented our six 18 metre nets in the pool ride with thirty metres of mist nets in the scrub. The birds weren't as obliging as the previous visit with eighteen birds processed from the pool nets and only twelve from the two extra nets.

Juvenile Cetti's Warbler

Our final total of thirty included twenty-two juvenile birds among them a Cetti's Warbler and a Goldfinch. The birds processed this morning were a Song Thrush, a Dunnock, a Sedge Warbler, a Wren, a Cetti's Warbler, two Robins, two Goldfinches, four Willow Warblers, four Whitethroats, five Chiffchaffs and eight Reed Warblers. 

Juvenile Goldfinch

At last a juvenile Cetti's warbler .............

In order to try and maximise our capture of reedbed warblers at Oxwich, Barry Stewart and I visited Oxwich this morning.  Having arrived at around 05:30, we had five sixty-foot nets up by 06:15, allowing us an hour and a half of catching time before work.  The weather was perfect, with very light winds, although mist lingered for a while over the reeds and seemed to supress early bird activity.

Despite this, the overall catch numbered 28, of which 10 birds were reed warblers (two were retraps from previous sessions) and 7 were sedge warblers (all new birds).  Other species included two bullfinches (both juveniles), a song thrush and an adult female reed bunting, the brood patch of which was just beginning to feather over.  However, the star bird of the morning was a Cetti's warbler.  This is not an unusual species at Oxwich: there are several territorial males around the marsh, and birds were trapped in the spring.  However, the bird trapped was a juvenile, the only one of the year to date.  This provides strong evidence of breeding on the marsh, as the post juvenile moult of the bird was not well advanced, and there is no other suitable breeding habitat close by.

The Cetti's warbler is shown below.  The ten (as opposed to twelve in all other UK passerines) tail feathers characteristic of this species can be clearly seen.

Another interesting observation was the tail of this reed warbler (photo below).  While reed warblers are not a difficult species to age, the tail bar on this bird was incredible.  As young birds grow their tail feathers simultaneously, a strong fault bar (indicating a period of environmental stress) that goes across the tail indicates a juvenile.  Adults replace feathers sequentially.  Therefore, while individual feather might show fault bars, in adults these bars will not tend to line up.
The final photograph is of a song thrush.  The first for the site in 2013, and still in full juvenile plumage (the belly had not begun to feather up).

Owain Gabb

Wednesday, 7 August 2013

CES 10, WWT Llanelli

Cedwyn, Aaron, Ben and I completed CES 10 at WWT Llanelli today. It felt very Autumnal first thing with temperatures around 11 degrees C at 05.30am. Last year CES 10 produced 10 birds and today we caught 15. We had Wren x 3, Blackcap x 5, Robin x 3, Chiffchaff x 2, Dunnock x 1 and a Blackbird. 12 of the birds were juveniles, which was encouraging but the total birds caught is still very worrying. One of the Blackcaps, an adult male was part way through its complete summer moult in preparation for its migration albeit a lot do over winter in the UK. It was a good opportunity to examine and record the wing moult of the primaries, which were 5554210000, a total score of 22. Both wings were checked and they mirrored each other. The head and body were also in heavy moult and 8 tail feathers were missing.

Maybe not the highlight, but the most exciting moment of the day was a buzzard that had been calling for most of the morning and then landed a few metres from the ringing station. It flew off low in the direction of nets 1,2 and 3 and I have never seen Cedwyn move so fast in anticipation of it being caught in one of them, only to be disappointed.

Downloading the pictures this evening to produce this blog I was very surprised to see someone had been busy using my camera. As you can see the early start had got the better of me.

Saturday, 3 August 2013

Oxwich Marsh: early August warbler movements ...

Despite some showers around dawn, the weather was good at Oxwich, only becoming breezy at around 09:30.  A total of five sixty-foot nets resulted in an overall catch of 40 birds, most of which were trapped in the first couple of hours.  The catch included 20 sedge warblers, 11 reed warblers, 2 blackcaps and a range of other species including reed bunting, robin, wren and blue tit. 

The highlight of the session was the capture of a juvenile grasshopper warbler, the first caught at the site in 2013.  This bird was carrying significant fat (fat score 5), indicating it was feeding up prior to migration.  Fat is assessed using a scale ranging between 0 (no visible fat) and 8 (a layer of fat overlying all of the breast muscles), and can be easily assessed by blowing the breast feathers to expose the underlying skin.  The fat score for this bird (5) indicates that the tracheal pit was full (convex), and fat was slightly overlapping the breast muscles.  A picture of the bird is below.

Sedge warbler has not been commonly captured at Oxwich this year: the number of territories around the reedbed earlier in the season appeared to be low.  This, and the extensive fat deposits visible on many of the sedge and reed warblers trapped, indicated that these birds had predominantly moved into the reedbed to feed up in preparation for migration (and were unlikely to have bred close by). 

Fourteen of the sedge warblers were juveniles.  These typically showed very little wear in the wing feathers and tails (some of which also showed fault bars and castellations).  Fault bars that run across all of the tail are indicative of juvenile birds, which grow their tail feathers synchronously.  Adult birds replace tail feathers one-by-one, so while individual feathers may have fault bars, these are very unlikely to form a continuous line.  Castellations are 'nicks' in tail feathers thought to result from damage in the nest. 

Oxwich is an excellent site for reptiles and invertebrates.  Today, a hummingbird hawkmoth was seen nectaring on bramble close to the ringing site, a buff tip (moth) caterpillar was moved from the adjacent road into nearby shrubs, and the hoverfly Sericomyia silentis (a substantial insect) was noted on ivy, where it posed for this photograph.  A brief search on Oxwich Marsh after the session resulted in three adders being seen.

Thanks to Keith Vaughton and Barry Stewart for making it another enjoyable session this morning.

Owain Gabb

Thursday, 1 August 2013

Kenfig NNR - CES 9

Heather, Chris and I made the best of the good weather to undertake the ninth CES - Constant Effort Site - session of 2013 at the Kenfig National Nature Reserve. We decided to supplement the 108 metres of mist-netting in the pool with an extra 30 metres in the nearby scrub which turned out to be a good idea as the additional nets produced the more birds.

Male Bullfinch

The usual CES nets produced six Reed Warblers, two Wrens, a Blackcap, a Willow Warbler, a Sedge Warbler, a Bullfinch, a Robin and a Whitethroat. The additional nets produced eight Blue Tits, four Great Tits, four Willow Warblers, two Whitethroats, a Reed Warbler, a Treecreeper, a Sedge Warbler, a Bullfinch, a Dunnock, and a Blackcap.