14th May - Ventnor - Bonchurch, Isle of Wight

Ian and I had discussed the possibility of this trip and with a very kind weather forecast we decided that this weekend was the day to put the plan into action.  I picked Ian up and we headed to Southsea to meet the first hovercraft of the day to Ryde on the Isle of Wight.  The sea was like the proverbial mill pond and looking across the Solent Ryde looked splendid in the early morning sunshine.

Why the Isle of Wight?  Well we were going to see if we could find the Glanville Fritillary, the area around Ventnor has one of the few colonies in the country of a butterfly that is numerous on the European continent, but very localised in the UK.

The crossing took ten minutes and we met our taxi outside the hover port, the drive took about 20 minutes and we were then getting ourselves set by the sea wall in glorious sunshine.

The day was all about the butterflies, for once the birds take a back seat.  We normally get to this point in June so it was pleasant to start early in the year.  

From the Winter Gardens we walked down to the path by the sea wall, looking for signs of lizards that also frequent the rocks under the cliff.  There was some movement around the edge of the path but no clear sighting.

The cliffs were covered in the red Valerian and across these small White butterflies drifted searching for others or just suitable flowers.  It didn't take long before the butterfly we were hoping to find appeared at the base of the cliff.

The Glanville fritillary is a beautiful orange and brown chequered butterfly that can only be found at a few locations in southern England, as well as on the Channel Islands. It's a sun-loving butterfly, which flies on warm days with little to no wind, and hides away amongst grasses on cooler, windier days.

Hopeful of finding more, we turned our attention to the other specialty here, Wall Lizards.  It did not take long and one appeared on the larger rocks at the base of the cliff.

The Wall lizard is very agile, and uniquely for British reptiles, can be seen running up vertical surfaces such as rock-faces or walls. It grows to around 20cm (8 inches) in length, with the tail making up around two-thirds of its overall body length.

There are two forms of Wall lizard within the UK: the brown-backed form which originated from western continental Europe (predominantly from Brittany, France), and the green-backed form seen here which originates from Italy.

There are around twenty separate colonies of the Wall lizard within the UK. These colonies are for the most part isolated and reasonably well self-containing. All these colonies are either associated with human habitation, such as Ventnor on the Isle of Wight, or with South-facing sea cliffs, such as most of the Dorset colonies.

Compared to native lizards, the eyes are set high on the head, and the snout is set high and rounded, resembling a small alligator

It needs wall cavities in which to shelter, but also loose stones at ground-level, under which the lizard lays its eggs. Some vegetation is required to support the food chain of invertebrates, but too much vegetation does not suit this lizard as it is a lover of sunshine and requires open bare areas.

All habitat locations within England are south-facing with long hours of sunlight, and are predominantly in the south of England.

Old stone garden walls are a particularly favourite habitat, although the wall must have a mix of vegetated portions and open basking spots. There should also be good vegetation at ground level to help to support the food chain.

So with 10 minutes of arriving we had found the two special species of the area.  There was definitely more to find and we set off walking the coast path towards Wheeler's Bay.

We walked along the sea wall which was glorious with the sparkling sea to our right and on the left and above us swards of Red Valerian flowers covering the slopes of the cliffs making a spectacular sight.

Red valerian was introduced in the 1600s from Europe but is now naturalised in the UK. Its pinky-red flowers grow from old walls, roadside verges, railway cuttings and cliffs, and provide nectar for insects.  It, has many regional names, given as the new plant grabbed toeholds throughout the land.

Due to its resemblance to lilac, and a lack of knowledge from where ever it came from, meant in the West Country it was American lilac, German laylock in Lincolnshire and wall lilac in Somerset. It was called pride-of-Fowey, or maids-of-Fowey, in Cornwall, and on the Isle of Wight it became known as Ventnor pride.  It will grow anywhere in poor, stony, well-drained ground, or in walls, and can be quite destructive as well as beautiful.

The cliffs and their base seemed to be a dumping ground for other non-native flowers, with orange and yellow asters and these wild Gladioli.

There was an area at the base of the cliffs that was fenced off, this was where the vegetation of the cliff broke up on the chalk.  The area was identified as in place for the benefit of the Glanville Fritillaries, but we were able to explore.

The first butterfly we found was this rather worn Dingy Skipper.

Then a flash of blue and the first photographable Common Blue of the year.

But the area was set aside for the Glanville Fritillary and if you build it they will come and they did, quite a few.in fact and showed really well in the sunshine.

The name "Glanville" is a tribute to Lady Eleanor Glanville, the 17th century naturalist who discovered the species. The butterfly was originally known as the Lincolnshire fritillary, as Lady Glanville first discovered the species in the Lincolnshire Wolds.

Eleanor Glanville is sometimes described as the first lady of British natural history; she studied butterflies at a time when it was considered improper behaviour for a respectable woman. After her death, Eleanor Glanville's family disputed her will on the grounds that she had lost her wits, as ‘nobody who was not deprived of their senses would go in pursuit of butterflies'.

The areas set aside for the Glanville is part of a major project to ensure the butterfly survives, as I have said it is an at risk species and under threat.  The main threats to the Glanville Fritillary are inappropriate coastal defence projects, which stabilise the eroding cliffs where it occurs, high grazing levels by rabbits or sheep, inappropriate tourist development and changes in the rate of erosion due to climate change. 

The immediate major objectives of the plan are to maintain viable networks of populations throughout its current range on the Isle of Wight, to conduct research on the distribution and ecology of the species and to continue the monitoring programme to enable its effective conservation.

Another new butterfly for the year to appear was a very smart Brown Argus.

But the Glanvilles kept coming.  A lady on the sea wall commented that there did not appear to be so many this year, but we were seeing many all along the base of the cliffs.

The Glanville fritillary favours habitats where the topsoil is regularly disturbed, allowing its larval foodplant (ribwort plantain) and nectar sources (such as dandelion, hawkweeds, bird's-foot trefoil, and thrift) to flourish. For this reason, it is often encountered on cliff sides, where the regular erosion of the cliffs creates the perfect disturbed conditions. The butterflies often form small discrete colonies, with little contact between them.

While the upper parts are an orange and black pattern similar to those on other fritillary species, the under wing is quite special

The special areas continued along the base of the cliffs and by now it was getting quite warm with very little wind, the cliffs providing shelter from any sort of breeze.

As well as the Glanvilles there were more Common Blue.

A Whitethroat sang from one of the bushes one the cliffs, it has been a lot of blogs since I only got to a bird photograph after so many others!

But it was back to the Glanvilles and more appearing now amongst the fallen chalk rocks.

On the Isle of Wight Glanville fritillary population numbers fluctuate wildly from year to year. In good times there may be thousands of caterpillars. But a poor year which may be due to unfavourable weather, a high rate of larval parasitism, or lack of the foodplant which causes te larvae to starve to death, or any combination of these will contribute to a major crash in numbers. The number of caterpillars though will gradually build up again after a crash and cycles last five or six years. There are thought to be 5-8 core colonies, which hold permanent populations and at which several hundred butterflies can be seen in a good year. During bumper years, Glanvilles form transient colonies elsewhere along the southern coastline and further inland, even reaching the northern coastline and across the Solent?  There once was a colony on Hurst Castle.

The coastal path then heads inland, with a climb up steps to the 11th century church, St Boniface Old Church.  Sunlight dappled through the surround yew trees lighting up the grave stones that were littered around the old church.  A Speckled Wood sunned itself on one of the stones.

We followed the coastal path until a diversion took us up onto the main road, we then headed to the west east end of Bonchurch Down.  A short rest and lunch was taken before we set of onto Bonchurch Down.  We decided to climb the down but before we set off there were more butterflies by the gate.  A Brown Argus.

And the first Small Heath of the day.

It was a steep climb up the down but with some commanding views away to the east and Bembridge.

At its height the down is the highest point on the island at 248 metres and commands views to Beachey Head and Portland on clear days.  Today the view was not as good as that but we could make out Portsmouth and the various landmarks along the Solent shore.

As the path leveled out we came across a Small Copper.

We followed the path at the top of the down but eventually need to head down.  At this point there were lovely views of Ventnor and St Lawrence Church.

It was difficult descending the steep slope, but we were distracted by more Common Blue and Small Heath. 

But as we reached the path at the bottom of the slope the Blues starting to become electric blue. It took some convincing as it was early but finally we managed to get a record of one and sure enough it was an Adonis Blue.  Here some with wings closed and just a glimpse of the electric blue upper wing.

Then finally a full view of those wonderful electric blues

This beautiful species of butterfly is one of the most characteristic of unimproved southern chalk downland, where it can be seen flying low over shortly grazed turf (typically steep, south-facing slopes).

The males have brilliant sky-blue wings, while the females are chocolate brown and far less conspicuous. Both sexes have distinctive black lines that enter or cross the white fringes of the wings.

Here are some Common Blues for comparison.

But there were also very good numbers of Glanville Fritillary here.

The Glanville fritillary favours habitats where the topsoil is regularly disturbed, allowing its larval foodplant (ribwort plantain) and nectar sources (such as dandelion, hawkweeds, bird's-foot trefoil, and thrift) to flourish. For this reason, it is often encountered on cliff sides, where the regular erosion of the cliffs creates the perfect disturbed conditions. The butterflies often form small discrete colonies, with little contact between them.

Ian then found a pair in the act of courtship, locked together and allowing some really close views

The Glanville fritillary butterfly lays its eggs on ribwort plantain in a warm, sheltered site. The caterpillars have a distinctive black body and red head, and emerge in February or March. They feed almost exclusively on ribwort plantain with a voracious appetite. They prefer the young plants that tend to be found where the cliff is crumbling away and there is little competition from other vegetation.

The butterflies emerge from the pupae in late May and June, but have a lifespan of only a few weeks. They feed on nectar from cliff-top flowers such as wild carrot, thrift and bird’s foot trefoil.  Glanvilles found along the sheltered, southeast-facing Ventnor coastline may emerge two or three weeks earlier than at other sites and are more frequently seen in early May.

We had really been given a special day and not a bad one for my first UK Glanville Fritillary.

But there was to be more, this time coupled Adonis, which I found amazing as I can't believe these butterflies have been emerged that long.

The white, textured disc-shaped eggs are laid singly under young, unshaded Horseshoe Vetch leaves in May-June and August-September. They can be found most easily in September where unshaded Horseshoe Vetch is growing on short turf.

The Adonis Blue overwinters as a caterpillar; it is is green with short, yellow stripes, which camouflage it while it feeds on Horseshoe Vetch during the day. It is most commonly seen during April and late July as it searches for ants to 'milk' its sugary secretions.

In April-May and July-August the caterpillar forms into a chrysalis in small crevices or hollows and is then buried by ants in earth chambers connected to the ant nest. The ants constantly attend to it for around three weeks, protecting it from predators.

This species has undergone a major decline through its entire range but, despite its restricted distribution, on good sites it can be seen in many hundreds, as it has recently re-expanded in some regions. Of concern is the current loss of grazing by rabbits, for example, causes the sward to become overgrown and can render a site unsuitable for this species.

Colonies vary in size considerably from year to year, depending on the weather. Many thousands can be seen emerging towards the end of a hot summer, contrasting with under a hundred from a spring emergence.

It is in flight when the electric blue shows at its best and I had a go at capturing the colour, this is the best I could do.

Our walk was now nearing an end and we followed the path down through Holm Oaks a very Mediterranean species.  Coming out at the bottom there was an open glade and as we reached the end of the walk we were presented with yet another Glanville Fritillary, what a day!

So after a celebratory pint we headed back to the taxi pick up and then back to Ryde for the hovercraft, it had been a very special butterfly day with 14 species seen