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.

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.

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