2015 British butterflies – 8: Glanville Fritillary at Hutchinson’s Bank, Surrey – 30th May

Britain’s rarest Fritillary has its stronghold on the south coast of the Isle of Wight, but has also been introduced at sites in south-east England. I interested Ewan in going to the IoW to see them but went off the idea on finding the ferry fare for a car and two people is £70. In the meantime Adam had told me about a site near Croydon where the species was introduced in 2011, so Ewan and I went there instead today.

Hutchinson’s Bank (TQ381616) is a London Wildlife Trust reserve covering an extensive area of a dry chalk valley. The steep grassland slopes support a diverse flora and up to 28 butterfly species. We left Oxford in reasonable sunshine but arrived on site mid-morning in largely overcast conditions. Entering the reserve from the end of Farleigh Dean Crescent (CR0 9AD), off Featherbed Lane we joined a group of observers from far and wide who were staking out a sheltered area of the track that they said is a Glanville hot spot. But some people had been there for a couple of hours without seeing any.

A man who seemed to know the site well then suggested another location and most people followed him. Through the next gate and around a few corners we came across an observer who had found a Glanville Fritillary near the valley bottom. This butterfly was perched open-winged on the ground to absorb what warmth it could and hence allowed a close approach. I feared a scrum but each person present took their turn to photograph the insect and so my own pictures were secured.

Glanville Fritillary

Glanville Fritillary

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This was the only Glanville we saw today though 39 were reported a week earlier. Emergence typically begins in mid-May and peaks in early June before numbers decline quickly, so there is a limited opportunity to observe them. The species has long been extinct on the British mainland and introductions have generally been short-lived. The Wrecclesham colony was wiped out by the wet summer of 2012 and I learned today that site is being developed.

Hutchinson’s Bank also supports good numbers of Small Blue. Here’s the underwing shot that I didn’t manage at Hagbourne two days ago. And then there was the big handsome fellow at the bottom – it’s a Roman Snail. Breakfast anyone?!

Small Blue

Small Blue

Roman Snail

Roman Snail

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2015 British butterflies – 7: Adonis and three more Blues at Oxon sites – 27 & 28th May

A further sunny forecast for much of yesterday afforded an opportunity denied so far this year to survey my “home reserve” Aston Rowant NNR (N) for spring butterflies. The top target was the iconic Adonis Blue that has established a reliable colony on the hillside above the M40 since I first observed them there in September 2012. But so far in 2015 I had not recorded other key species such as Brown Argus and Small Heath in Oxon, Bucks and Berks (BC UTB area) and that also needed to be addressed.

The downside of this site is that cloud often stacks up on the Chilterns escarpment, so butterflying can involve a little too much waiting for the sun to break through. This morning was no exception and hence in the first couple of hours I found just a few each of Common Blue and Brown Argus and a lone Dingy Skipper. While waiting on a slowly approaching patch of blue sky I walked a circular route around areas of the reserve that I don’t usually get to, being reminded of the sheer quantity of superb butterfly habitat that exists here. I timed this excursion well, arriving back at the area where I expect to see Adonis Blue just after the sun had broken through, but none of that species were to be seen.

Just after midday blue skies came to prevail and though I was two-thirds of the way back to the car park I just had to go round again. With the hillside now bathed in sunshine Common Blue and Brown Argus (that is another blue) were suddenly flying in great numbers, and some Green Hairstreak were emerging at the brambly foot of the hillside. I also found a first Small Copper of 2015 and first in-area Small Heath as I retraced my steps to the Adonis hot spot, but a second scan there was no more productive than the first.

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Then on going back through the gate at the end of the sunken way trail, there were three male Adonis Blue on the wing. In the picture (above) I usually expect to see them on the far side of the fence that runs down the hillside. But yesterday they were on the near side where though the grass was longer there was plenty of the food plant Horseshoe Vetch. Two of these butterflies allowed a very close approach, when they weren’t being harassed by aggressive little Brown Argus, and hence mission was accomplished with good pictures.

Adonis Blue (male)

Adonis Blue (male)

The double-brooded (late May and August) Adonis Blue is localised throughout its range on southern English chalklands. The vivid colouring of the males usually makes them stand out at some distance though this can range from turquoise to violet, confusing separation from the deeper violet and far more numerous Common Blue. The fine black lines crossing the outer white fringes and just entering the body of the wings, that the above picture clearly shows, are a diagnostic feature. The year’s first Adonis Blue were also reported at two more key BC UTB sites, Lardon Chase (Berks) and Yoesden Bank (Bucks) on 27th May.

I know of several sites in south Oxon where the diminutive but fascinating Small Blue may be found. My favourite hot spot is just south of Lowbury Hill on the border with Berkshire, the highest point on the downs above Blewbury. But this involves a 5-mile walk out and back that just invites sod’s law to roll in the grey stuff upon arrival. Today was not one to risk it so instead I visited the easiest accessible site Hagbourne Railway Embankment (SU622894). This former branch line, now a designated cycling route and permissive footpath, is a gem of a butterfly site in high season being very wild flower rich. And it has two specialities: Essex Skipper and Small Blue.

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Though widely distributed the latter has a need for sheltered locations, old quarries and steep embankments being favoured habitats. Blustery conditions this afternoon meant they were unlikely to be flying on the western side of this particular embankment where I usually find them. But about halfway along the route is a feature (pictured above) where tarmac access paths split the eastern slopes. Hence the more sheltered habitat here was easy to scan and indeed I found two of Britain’s smallest butterfly. These were difficult to capture in the long grass but with persistence I gained an acceptable record shot (below).

Small Blue

Small Blue

2015 British butterflies – 6: Wood White in Bucknell Wood, Northants – 26th May

The rarest British white is almost extinct in my home area of Oxon, Bucks and Berks, but thrives in a number of woodlands in Northamptonshire. One of these, Wicken Woods straddles the border with Bucks but my location of choice is Bucknell Wood (SP660451) just outside of Silverstone off the A43. This is possibly out of laziness, having visited before in each season from 2011 to 2013, as the species is easy to find here and I know exactly where to look.

The road to this Forestry Commission woodland from Silverstone is currently closed, necessitating a diversion back onto the A43 towards Towcester, then left at the next roundabout following signs to Abthorpe. On my arrival today a first Wood White ghosted by in the car park. I then walked the main track westward as it was bathed in sunshine (below).

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I quickly began to see Wood Whites here and counted about 20 as far as the crossroads in the centre of the wood. These languid waifs have a dainty appearance and delicate flight that easily distinguishes them from Green-veined or Small White, and they are also smaller than those other species. As I fired off the frames from which to select the pictures below, all the frustration of a four day wait for sunny weather melted out of me.

Wood White

Wood White

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Wood White is localised in southern England and rarely numerous where it does occur. The black wing tips of the males seemed more noticeable today than on my previous visits to this site. These are very apparent in this picture of a courting pair (below).

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Having gained such a good result along just part of the route I usually walk here, and mindful of the need to return to Otmoor, I decided against going further into the woods. If anything there seemed to be more butterflies on the wing as I walked back to the car park.

Dainty, delicate, ghostly and languid

Dainty, delicate, languid and ghostly

Hairy Dragonfly and more Otmoor Odonata – 25 & 26th May

The present weather pattern is seriously frustrating my intention of presenting full English butterfly and Odonata years on this blog. But at around 9am this morning, after four days of bright starts then blanket cloud, I was pleased to see bluish sky stretching away to the north. So I set off for Otmoor hoping to photograph Hairy Dragonfly if insect friendly conditions persisted through the morning. On arrival at the Noke End of the Otmoor bridleway (SU553130) it was quite sunny but not even damselflies were on the wing. So I decided to prioritise my next butterfly destination in Northants then come back here later.

Noke with Otmoor beyond

Noke with Otmoor beyond

Returning in the early afternoon, Otmoor was indeed still bathed in sunshine (pictured above) as I turned off the B4027 and headed down to Noke. But as ever on reaching the bridleway what cloud there was managed to cover the sun for a while. No matter, I soon found a male Hairy Dragonfly that was perched low down in cover to one side of the track. The record (below) is the sort of clutter-filled picture I usually try to avoid but I was just pleased to have captured a 2015 Hairy at last.

Hairy Dragonfly (male)

Hairy Dragonfly (male)

Hairy Dragonfly (female) (c) Gareth Blockley

Hairy Dragonfly (female)
© Gareth Blockley

On Saturday morning a female Hairy was photographed here after apparently allowing a point blank approach in the overcast conditions. I disturbed possibly the same insect a day ago but she saw me before I noticed her and promptly relocated to the far side of a drainage ditch. This species clearly does not perch openly like it’s late summer Southern and Migrant Hawker counterparts, and as Emperor and Brown Hawker do will move quickly to safety on being approached. As if to prove the point my next sighting was a mating pair of Hairy that flew out of a Hawthorn on one side of the path to be lost in a hedge on the other side.

After a slow walk eastward along the bridle path there were a third male Hairy and two Four-spotted Chaser north of the cross roads. I hoped the shelter behind the hedge here might produce more sightings, but the day was soon past its peak weather-wise. So with the grey stuff settling once again over Otmoor I retraced my steps to Noke more quickly than I had come. In my haste I put up a fourth male Hairy and this one settled again within a short distance. The picture (below) is a bit less grassy than the first but still not satisfactory. I will hope for better results in the days ahead.

Hairy Dragonfly (male)

Hairy Dragonfly (male)

On Monday (25th) once I had lost the female Hairy Dragonfly, only Damselflies were active in the overcast conditions and I paid more attention than usual to them. Most of these were Azure Damselfly, with occasional Blue-tailed and Red-eyed Damselfy.

Oxon birders sometimes tell me they can’t be bothered with these insects and when I first took an interest in Odonata I also thought it too much trouble to separate the various female and teneral (immature) forms. But once I started to compare my own photographs with field guides it all became more interesting. The three damsels in the lower row are all female Azure for instance, there being a variety of forms. And a cloudy morning without butterflies or dragonflies for distraction was as good a time as any to indulge all of this a little.

Otmoor Downy Emerald and other early season Odonata – 21st May

A day of prolonged sunshine in late May isn’t too much to expect is it, even in Blighty? Well it’s all depended on how far south the jet streams flow in recent years and 2015 has been a familiar story. In another week of unfriendly conditions for observing insects today actually delivered some fair weather and results. And I realised an important ambition for this season of finding and photographing Downy Emerald on my local nature reserve, Otmoor.

This most beautiful of dragons, Four-spotted and Broad-bodied Chaser have all been recorded on the reserve on other recent sunny days when I have been away seeing to my 2015 butterfly series. Setting out this afternoon along the Roman Road footpath that runs north from the end of Otmoor Lane, I was quickly rewarded with a season’s first Four-spotted Chaser. Then on either side of the corner where this path meets the eastern end of the Otmoor bridleway at least three Hairy Dragonfly were active. I saw my first local Hairy at this same spot three days ago but as on that occasion today’s didn’t perch in the open to oblige for the camera.

Downy Emerald and friend

Downy Emerald and friend

Not so my first ever Otmoor Downy Emerald (above). Having been disturbed initially by one of the Hairys, allowing me to locate it, this Downy then basked in sunlight in the same spot for a very long time. Eventually it disappeared in a moment when I was distracted by another Hairy fly-past. This metallic green species breeds in standing water close to woodland and often hangs down from branches as this one did when at rest. Otmoor is now a reliable site though they occur only in small numbers and luck is required to see one.

There were at least three Four-spotted Chaser in the vicinity, a very widespread species that is always easy to photograph (below). The Hairys continued to come and go but not settle within range, and I saw another three when walking back up the Roman Road to the car park.

Four-spotted Chaser

Four-spotted Chaser

Numbers of blue damselflies are also building along the Roman Road. In my two visits here this week they all looked like Azure Damselfly, though as usual occasional Large Red Damselfly put in appearances (see Downy photo). This site will be teeming with common damselflies before very long, allowing comparison of several similar species in different forms. Two days ago at the Noke end of the Otmoor bridleway I came across a first Red-eyed Damselfly of the season.

Sum plum stars at Farmoor Reservoir, Oxon – 14th May

When my plans for this morning fell through I was pleased to get an Oxonbirders’ text alert saying there was a Black-throated Diver at Farmoor Reservoir. I jumped into the car and went at once, this being a bird I have seen twice before but not in summer plumage. In the event I was the first local twitcher to arrive on site, and patch watchers Dai and Steve walking back along the central causeway told me the bird was diving close to one side of the famed concrete bank.

Rain having begun to fall on my arrival I had left my camera in the car and realised that in choosing to do so I had missed a good photo opportunity. Once company arrived and the bird drifted into the middle of F2 this error of judgement caused a few wry looks and the county bird recorder suggested I use a carrier bag in future. Very apt advice and why didn’t I think of that? We all watched the BTD for a while then Dai (who has a vehicle permit) returned to get the bird onto his dog Billy’s Farmoor list (see here). So he kindly ran me back to the car park where I swapped my scope for my camera (and carrier bag).

On my return the BTD was being watched close to the causeway hide. Once the others had returned to work or wherever they had to be, myself and one other birder who said he shouldn’t be here were left to watch the bird drifting first one way then the other close to the hide. I was then able to experiment with different camera settings and get what with my equipment were reasonable shots (above). At times the bird would stand up in the water and preen, behaviour I have not observed before.

In the past couple of weeks I have also noted with envy various county birders’ pictures of summer plumaged Sanderling at Farmoor. But whenever I dropped in there were none of this species present. Spotting one today on the opposite side of the causeway I added more reasonable results to my Farmoor waders’ gallery. As usual the sludge and detritus of the reservoir shoreline provided a subtle background to the subtler and delicate tones of this beautiful passage migrant.

Sanderling

Sanderling

I think I am right in saying the reaction of everyone who saw the BTD today was “cracking bird!” I can only agree on both species and all this was a most excellent way of passing a wet spring morning. The BTD remained at Farmoor for nine days but observers realised it had picked up an injury and wasn’t well. Sadly this bird was found dead on 23rd May.

2015 British butterflies – 5: Marsh Fritillary and much more at Cotley Hill, Wilts + Wall Brown – 13th May

The key species are coming in thick and fast now. When I read that Marsh Fritillary were flying at my site of choice there was only one place to go on this warm and sunny day. In my home area of Oxon, Bucks and Berks there is just one tiny and fragile cluster left. Not too far away in Wiltshire variable concentrations of the species can be found, and Cotley Hill (ST917427) near Warminster must take the title of Marsh Frit grand central. My visits here in 2011 and 2013 yielded large numbers of what is a declining and distinctly localised butterfly nationally, and today was a repeat experience.

From a lay-by at a roundabout on the A36 near Heytesbury, a footpath leads uphill into a long south-west facing slope covered by unimproved grassland. This site supports a rich flora and 29 breeding species of butterfly. Taking the first sheep track left at the foot of the hill I quickly began to see Marsh Fritillary, as on those previous visits. An observer walking back told me there were hundreds on the hillside above and indeed there were. This butterfly has a pleasing habit of sitting up and keeping still for the camera, and one after another did just that as I walked around.

Marsh Fritillary

Marsh Fritillary

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Marsh Frit can be very variable, the smallest males being a fraction of the size of the largest females. Although the chequered pattern is constant the wing colours can also vary a lot. Underwing shots are more difficult to come by. This newly emerged female (below) was still drying in the sun while already rejecting the attentions of a male suitor.

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The supporting cast here was a check list of April and early May key species: Dingy and Grizzled Skipper, Green Hairstreak, Brown Argus, Small Heath and my year’s first Small Blue.

There was still time for a bonus butterfly so I walked up the main path and back to look for Wall Brown, having seen them here previously and at other Wiltshire sites. This species is virtually extinct in my home area. Back at the lay-by a Wilts man gave me directions to another location where he said they fly. About ¾ mile west of Avebury on the A4 is a lay-by on the south side of the road from where a footpath leads uphill through a Beech copse. On the eastern side of this, above some racing gallops is a worked out chalk pit with an exposed chalk bank. And here indeed I encountered this rather splendid Wall Brown (below).

Wall Brown

Wall Brown