Thursday, 17 August 2017

Mid-August at Castle Hill LNR, Newhaven

Week 20 of the Castle Hill LNR butterfly survey season

Rampion off-shore windfarm in progress - as seen from the Castle Hill LNR clifftop
Seed-spangled orb web
I did my transect walk on Sunday in better weather conditions than I've had recently. We're at week 20 of 28 already. I've added below a list of what I saw. Most of the flowers are now past their peak, but there is still a mass of late-summer colour. The willowherb was casting immeasurable numbers of seeds into the air and all the spider webs were spangled with them.
There were 25 species of butterfly and moth and a total of 438 individuals, which I thought was pretty good considering the time of year. I was particularly pleased to see 27 Small Heaths; it has never been a common butterfly at Castle Hill LNR and has significantly declined in the UK over the past few decades, mainly because of the loss of habitat as grazing land has been 'improved' for livestock. It is a butterfly that likes fine grasses on dry soils and Castle Hill offers some good potential habitat, particularly along the clifftops.  Annual totals since 2011 have been 3, 7, 12, 23,31 and 37, so to have seen 27 in one day, mostly along the clifftop, is great news. It has been having a good year generally and I have been counting up to 80 on some days in a meadow near The Rookery at Bishopstone.

Small Whites were seen in good numbers; it was strange to have seen 60 and not a single Large or Green-veined White to go along with them - I wonder what the odds are of that?! Clouded Yellows are beginning to make an appearance and Holly Blue numbers were good along the northern path.
Volucella pellucens - the Pied Hoverfly
Amongst the other stuff seen were quite a few Volucella hoverflies. V. zonaria and pellucens are among the most spectacular of the 7000 species of British fly. A female Wheatear was seen on the clifftop, indicating that the autumn migration is upon us. Another year if flying by!

Butterflies (13 species)

Small White
Pieris rapae
Clouded Yellow
Colias croceus
Speckled Wood
Pararge aegeria
Small Heath
Coenonympha pamphilus
Meadow Brown
Maniola jurtina
Pyronia tithonus
Red Admiral
Vanessa atalanta
Painted Lady
Vanessa cardui
Inachis io
Small Tortoiseshell
Aglais urticae
Polygonia c-album
Holly Blue
Celastrina argiolus
Common Blue
Polyommatus icarus
Moths (12 species)

Bordered Carl
Coptotriche marginea
3 (mines)
Common Nettle-tap
Anthophila fabriciana
Ox-tongue Conch
Cochylis molliculana
Common Marble
Celypha lacunana
Grey Gorse Piercer
Cydia ulicetana
Six-spot Burnet
Zygaena filipendulae
Straw-barred Pearl
Pyrausta despicata
Small Purple & Gold
Pyrausta aurata
Common Purple & Gold
Pyrausta purpuralis
Rush Veneer
Nomophila noctuella
Straw Grass-veneer
Agriphila straminella
Silver Y
Autographa gamma
Other stuff

Common/Viviparous Lizard
Lacerta vivipara
Falco tinnunculus
Accipiter nisus
Wheatear (female)
Oenanthe oenanthe
Southern Hawker
Aeshna cyanea
Pied Hoverfly
Volucella pellucens
Hornet Hoverfly
Volucella zonaria

Monday, 12 June 2017

Hunting Nightjars at dusk

The woodsmen of the Sussex Weald walked out of the trees long ago now, taking their coppicing tools and charcoal burners with them and leaving their woodland clearings to the relentless green succession. This Wealden wood is a remnant of the great Andredesweald forest of the South Saxons – Lindhersse to the Normans, who gifted it to Battle Abbey and rechristened it The Abbot’s Wood. Banks and ditches and great marker trees offer clues to the antiquity of the place. The Forestry Commission is the current steward of the trees. Dark conifer plantations have been felled and replanted with native broadleaved oak and hornbeam interspersed with hazel, sallow and birch. Dormice and Pearl-bordered Fritillaries are two species who benefit. We are visiting this twilight to find another: the fern owl, goatsucker, dor-hawk of country folk; Caprimulgus europaeus to science; the nightjar.

The sun has set; the full moon has risen but cannot yet be seen above or through the encircling trees. A breezy day has beclamed and the hazy sky softly glows in a palette of pastel shades. With a growing sense of expectation, we step into the gloaming. There is light enough to spot warblers and thrushes still feeding their nestlings. A great-spotted woodpecker emerges from the trees. Moths rise earlier here; I follow Agapeta hamana until it settles, Cochylis lacunana too.

We zig-zag our way along narrow woodland rides until a gap opens out into a wide clear-felled area. Blackbirds, song thrushes, nightingales call across territories; distant corvids pass; gulls make their easy glide coastbound. Low cloud is hugging the downs and the weather there is less clement there than here. I give silent thanks. We meditate to the thrushes’ poker song (I'll take your notes and raise you something slightly more complex. Well I'll take yours and do the same). From above and behind our right shoulders a large, silent silhouette glides across us. Its long tapered wings, an underside speckled white and dark, the unmistakably-shaped face. Our first nightjar – a female – appears and is gone almost before we know it. The time is not much after nine. Low to the south the small full moon is glowing through a wash of gossamer cloud.

In the distance the churring call of one or more nightjars waxes and wanes, undulates, stops, begins again. It is almost a growl. The name: nightjar; I cannot help but hear the woodsmen of old call the beast noightchurr as they made their way home from the clearing, leaving the gloaming beasts to the tightening murk. It is their time of day, not ours. No wonder it's the stuff of myth, a beast that sucks the milk of goats. Sometimes it's too dark to tell what the truth is.

The appeal of this bird skulks in the twilight, the enigmatic hour of shifting shadows, wherein mysterious beasts lurk. Winter is spent in Africa, south of the Sahara. A recent study found that British nightjars migrate to and from the Congo. It is close to ten now and we begin making our way home.

The path is a black ribbon. Dark clods plop around us in the murk, small toads on closer inspection. Approaching home we are diverted by screeches from a large oak which splays its branches above the path. They are tawny owlets, two of them. Close by and louder, the churring resumes in a clearing behind the big oak. One, then two or more churrs pulsate through the air before trailing off into silence, then a wing-clap, then the silhouettes of a first, second and third nightjar swoop around us. It's a perfect coda.

Wednesday, 19 April 2017

Overwintering moths and butterflies: three years of tunnel surveys at Newhaven Fort

We completed our third winter of surveying moths and butterflies in the tunnels at Newhaven Fort in February. The previous two years set a trend in which our first visit in mid-December produced better results than the second in early or mid-February. That trend was bucked in February as we saw a better return than any of the previous visits.

Why? There are environmental variables at work which affect the numbers of insects that we see. These include day length, seasonal weather, population abundance prior to diapause (and the many factors affecting seasonal abundance), the activity of predators and pathogens during the winter, and unintentional human disturbance (e.g. use of artificial lighting). The tunnels are a suitable hibernaculum during the winter because they are dark yet they still indicate changes in day length, they are ventilated and the temperature is cool and fairly stable. The tunnels offer protection from environmental shocks such as sudden cold snaps, flooding, strong winds and the potential disturbance or destruction of habitats. The tunnels offer a fairly stable environment and catastrophic change is less likely; therefore the instincts which drive insects into places like tunnels are more likely to result in their survival. Any combination of these and other variables would have contributed to the abundance of moths and butterflies we saw in February. The autumn saw an extended period of warm and dry weather. The 2016-17 winter was cooler than the two previous years and there have been more frosts. The cool winter weather extended to the day or two prior to our February visit. These are likely to have influenced the numbers we saw and might help to explain why we saw significantly more this February than in February '15 and '16.

Here's a summary of the six visits we have made since December 2014, which allows us to compare numbers of each of the seventeen species we've recorded during the three year period. The most important species we've seen is the Bloxworth Snout (Hypena obsitalis) and this is the main reason for the survey. It has been present in consistent numbers during the first three years of the survey and marks Newhaven Fort out as one of the best-known sites for this moth. Larvae have yet to be found, but its foodplant Pellitory-of-the-wall (Parietaria judaica) is present at the Fort and Castle Hill LNR and it is tempting to think that it is breeding locally.

Saturday, 15 April 2017

A haunting at Burnthouse Bostall

 December 2012.

The well-shaft has been cordoned off with wooden stakes and health and safety bunting; it flaps in celebration of the well's return from the dead. It is darkening, damp; that rapturous time between Christmas and New Year when people pause to reflect on things gone, when the world is suspended and time teeters on the turning year, turning away from darkening days back towards the light and the return of life.

Three centuries ago the water left Burnthouse Farm and the well was a useless empty receptacle, it's flint lining dulled and silenced. As the water ebbed, darkness rose. Three centuries back, back beyond the eye of the archaeologists' census, this aged hole dug by hand, many hands perhaps, reaching down to life-giving water, where it sustained man and beast for a time, only to have left again to follow the springline elsewhere, cutting its life-blood, leaving the well-shaft empty, forgotten, capped and darkened. The forgotten well has come to light again now only when the light returned, when the water returned, both seeping back in, making heavy the waterlogged turf, the thin rendzina above the rotten timber well-cap, hyphae-riddled, weak and unable to resist the irresistible urge of homecoming, of stirred memory.

I was here once, I can hear the watery whisper recall as I ponder the hole. Someone deeply dug this shaft, toiled no doubt to urge pure water in through filtering chalk, at the spingline near the downland foot, water to sustain and give life, to keep the farmstead flowing. I was once here; the stirring of memory ripples through its calm progression, interrputing its silent cascade down the chalk to the wealden clay. It pauses and feels its way over the well-cap, trickles through the turf and humus, touching the timber, tasting the rot, settling its weight across to feel the void beneath. The heavy draw of homecoming is too great, the cap yields and the ground across the path becomes a well again. A rapture in reverse, a gift to us from above, from the falling rain.

Water forgot this place but its memory was rekindled. Without the water the well would have remained a secret beneath the light tread of walkers' feet. The water left, Burnthouse Farm died and all but the bostal forgot. But the water has returned and given the well new life, returned it to the people, to right a wrong, I fancy, that once killed a farm and sent its people away from this place of abandon. This is the water's gift. It doesn't need to dwell. It gives thanks to the toiling hands which once faithfully reached down to it. Without this water we might never have known the well. It haunts this old place so that we may know it. This is its gift.

Sometime on 30th December 2012 a small patch of downland turf near the foot of Burnthouse Bostall in Westmeston, at OS grid reference TQ3221359, collapsed. Someone dragged a fallen tree across it. The ancient well was not previously known and was absent from the archaeological record. Heavy rainfall running down the chalk escarpment formed heavy waterlogged ground along its foot and the old well-cap could not withstand the pull of gravity. The Environmental Health out-of-hours duty officer built a cordon around the exposed well-shaft with the Chair of Westmeston Parish Council. I kept a vigil when my duty-officer shift began to ensure no further collapse occurred. I reported the collapse to the land owner (the National Trust) and reported the well's existence to the County Archaeologist, who confirmed that the well was unknown and therefore likely to be at least three hundred years old.

Friday, 14 April 2017

Pollarding at Charleston Reedbed

Charleston Reedbed. What a lovely little postage stamp of a wildlife reserve! Small yet criss-crossed with a warren of reed- and scrubby woodland-bounded, water-bounded paths, this privately-owned patch of land, secured by the master of Eastbourne College in the 1930s to protect it from development, welcomes volunteers to winter work parties. I took the opportunity in mid-March to explore the reserve and spend a half-day pollarding willows.

For a small reserve, it quickly became apparent that there is a lot of activity here. The site's appeal has a wide reach. An array of neatly rolled mist nests informed me that this is an important bird-ringing site. Amongst the group of fellow workers were several people I know from various corners of the wildlife and conservation community, including keen bird-ringers. Tim and Sue were in charge. Their first piece of advice was offered very clearly: "Stick to the paths". A deviation to the side might well send you waist-deep into water. Some of the paths themselves had been laid with pallets and boardwalks where the water held sway over the land.

Our task was to check back the growth in successional vegetation; the many willow trees: sallow, grey willow and osier. Their thin 'withies', the whiskers and whips which sprout from the pollards, quickly thicken and drink up the squelch from the wet ground. This threatens the reedbed, the whispering Phragmites, which would be succeeded by fairly quickly by a wet but drying woodland. We spent two or more hours cutting and dragging the withies to a site where they will season before being burnt.

We broke for lunch and shared recent wildlife sightings, chatted about aberrant farmers and wildlife legislation after Brexit. Expecting to return to work, I was surprised by the offer of a site tour instead. We had cut back all that was required for one day. With the calls of Cetti's warblers and chiffchaffs, dunnocks, blue tits and goldfinches, Tim led us around and explained how thick blackthorn scrub had been eradicated by cutting it to the base, leaving it for two years to sprout anew and then treating it with glyphosate, and how reeds in some areas are cut back every three years.

Stigmella aurella mine on bramble
My eyes are inevitably cast downwards, in pursuit of moths and their signs - attuned to their bilinear symmetry, as a friend recently (and perfectly) described it. The silver gallery mines of Stigmella aurella were everywhere on the reserve that bramble occurred - on many of the leaves I encountered a silver river progressing in expanding breadth from source to glorious termination, pupation, the metamorphic flow from larva to imago. It was too cold and grey for butterflies; the optimist within pined for an early season Brimstone to emerge from the vegetative thatch in which it overwintered and to dart through the osiers, but none were expected nor seen. A single moth was seen: an Acleris hastiana, or Sallow Button; my first sighting of this species for five years and only my third ever. This is one of the most variable Tortrix moth species and, although I couldn't name the colour form, it was one that was new to me.

Like the ground beneath the willows, cutting through the withies was soft work, even when the loppers had to be downed for the bowsaw. Soft, enjoyable work and easy company and within walking distance of home. I shall return.

Whispering Phragmites