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	60
Clouded Yellow	Colias croceus	4
Speckled Wood	Pararge aegeria	29
Small Heath	Coenonympha pamphilus	27
Meadow Brown	Maniola jurtina	129
Gatekeeper	Pyronia tithonus	19
Red Admiral	Vanessa atalanta	3
Painted Lady	Vanessa cardui	4
Peacock	Inachis io	1
Small Tortoiseshell	Aglais urticae	1
Comma	Polygonia c-album	1
Holly Blue	Celastrina argiolus	6
Common Blue	Polyommatus icarus	127

Moths (12 species)

Bordered Carl	Coptotriche marginea	3 (mines)
Common Nettle-tap	Anthophila fabriciana	2
Ox-tongue Conch	Cochylis molliculana	1
Common Marble	Celypha lacunana	1
Grey Gorse Piercer	Cydia ulicetana	6
Six-spot Burnet	Zygaena filipendulae	1
Straw-barred Pearl	Pyrausta despicata	3
Small Purple & Gold	Pyrausta aurata	1
Common Purple & Gold	Pyrausta purpuralis	2
Rush Veneer	Nomophila noctuella	1
Straw Grass-veneer	Agriphila straminella	2
Silver Y	Autographa gamma	4

Other stuff

Common/Viviparous Lizard	Lacerta vivipara	2
Kestrel	Falco tinnunculus	1
Sparrowhawk	Accipiter nisus	1
Wheatear (female)	Oenanthe oenanthe	1
Southern Hawker	Aeshna cyanea	1
Pied Hoverfly	Volucella pellucens	1
Hornet Hoverfly	Volucella zonaria	4

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.

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

Migrant butterflies and moths at Newhaven: the last five years of recording

Painted Lady (Vanessa cardui)

I have taken a look at all the migratory butterflies and moths that I recorded in Newhaven between 2012 and 2016. The results are in the table below, which gives an overall total for each species for the five year period, a per annum average for the period and the annual total of each species from 2012 to 2016. The species in the table are organised in order of abundance over the five years.

Red Admiral (Vanessa atalanta)

Why do we see immigrating butterflies and moths and how do they get here? The thing with migratory insects is that the numbers seen on our shores are unpredictable from one year to the next. Some of the factors which influence the numbers of adults seen on UK shores are the success of each species in the previous year, the environmental conditions and survival success of the early life stages in their native land, the number of adults which migrate and the weather conditions during migration. For this reason, numbers seen in the UK tend to vary wildly from year to year, and this can be seen in the table below. Additionally, geography and location should be a consideration. I feel that Newhaven is at an advantage because of the Ouse Valley, which some species might use as a navigation aid. Other species such as Painted Lady congregate on hill-tops and the crest of the Bishopstone escarpment, which rises just north of the Buckle in Seaford and runs northwards along dry valleys toward the downs above Beddingham, is a good location for this species along with Diamond-back Moths and Rush Veneer.

Vagrant Twitcher (Tebenna micalis)

Another important caveat is recorder effort. If more effort is made one year and less another, this will affect the total numbers seen, so consistency is important. Recording methods can affect the results in a similar way. For example, a transect walk survey has been performed each week between April and September throughout the five year period. The walks are regulated by a code of practise which helps to achieve a consistent approach, so the data collected during the walks are of a high quality. Of less reliable quality are the numbers I have recorded at home in my moth trap. I have been more or less consistent in my approach during the five year period, but there are two considerations when analysing the data. Firstly, I changed the light source in July 2013 from a 2x30W actinic light (a type of UV light) to a 125W MV (mercury vapour) light. This is a significant change because many species are more strongly attracted to mercury vapour light than actinic, and this has been reflected in the results since the change in July 2013. Second, the number of nights that I have operated my trap each year has varied, as follows: 155 nights in 2012, 176 in 2013, 211 in 2014, 205 in 2015 and 209 in 2016, meaning there is a slight upward trend. This, too, will have influenced the data.

Rusty-dot Pearl (Udea ferrugalis)

One final consideration is that data collected at one geographic location (Newhaven in this case) cannot be representative of other locations and should therefore not be used as an indication of general abundance. It is a little like looking into a rock pool and assuming the same stuff will be found in every one. It isn't. However, large immigration events do tend to have a regional impact that produces similar results for some species at different recording stations. 

Looking at the table, the species in first place is the Diamond-back Moth (Plutella xylostella). Immediately we see the point proved about wild fluctuations from one year to the next. Last year (2016) was an exceptional year which saw a colossal immigration of probably billions of these moths. It feeds as a larva on crucifers (cabbages), so the immigration was not welcomed by farmers or gardeners. Bearing in mind that the moth is tiny (about 7mm long), it amazes me that it is able to fly any distance at all, but it is carried in large air masses long distances from its continental homeland.

There are a number of species which are regular migrants each year, including the Clouded Yellow (Colias croceus), Red Admiral (Vanessa atalanta) and Painted Lady (Vanessa cardui) butterflies and the moths Rusty-dot Pearl (Udea ferrugalis), Rush Veneer (Nomophila noctuella), Silver Y (Autographa gamma), White-point (Mythimna albipuncta), L-album Wainscot (Mythimna l-album), and Dark Sword-grass (Agrotis ipsilon). Of these, most had an average year in 2016, but Rusty-dot Pearl, Rush Veneer and Silver Y had a significantly above average year. The Silver Y famously made the news when one landed on the footballer Ronaldo’s face during the European Cup Final in July. It became an internet sensation (#mothonface). It should be noted that some of these species are also considered to be transitory residents (i.e. they gain a temporary foothold in the UK and breed successfully for a year or more before colonies succumb to environmental shocks). For these species (White-point, L-album Wainscot and Dark Sword-grass) the southern UK is at the very north of their range and they might form resident coastal populations in the future as a result of climate change. The L-album Wainscot has been breeding along the coast in Newhaven for some years.

Silver Y (Autographa gamma)

Species seen regularly in small numbers include the plainly beautiful Olive-tree Pearl (Palpita vitrealis), Hummingbird Hawk-moth (Macroglossum stellatarum), Gem (Nycterosea obstipata), Four-spotted Footman (Lithosia quadra), Scarce Bordered Straw (Helicoverpa armigera), Feathered Brindle (Aporophyla australis), Delicate (Mythimna vitellina), and Pearly Underwing (Peridroma saucia). Last year was a pretty average year for all of these.

The species which cause excitement in varying degrees when they appear include the Oleander Hawk-moth (Daphnis nerii), Blair’s Mocha (Cyclophora puppiliaria), Vestal (Rhodometra sacraria), Ni Moth (Trichoplusia ni), Bordered Straw (Heliothis peltigera), Small Mottled Willow (Spodoptera exigua), Clancy’s Rustic (Platyperigea kadenii), Oak Rustic (Dryobota labecula) – which is actually colonising eastwards along the south coast, Flame Brocade (Trigonophora flammea), and White-speck (Mythimna unipuncta). Most of these have appeared as singleton
sightings on very few occasions. The Vestal (Southern Europe and North Africa) and Small Mottled Willow (Europe) have behaved similarly by not being seen at all in three of the five years, but with a spike in numbers in 2015.

Convolvulus Hawk-moth (Agrius convolvuli)

Oleander Hawk-moth (Daphnis nerii)

The star of the show is the Oleander Hawk-moth which made its first appearance in Sussex for about 25 years when it appeared at Newhaven Fort in 2014. At least three were seen in Sussex in 2016 (including one mentioned below), but this is a moth of North Africa and Mediterranean islands, so do not expect it to become resident in the UK any time soon! It is a truly stunning moth and one of the best examples of how the beauty of moths can surpass that of butterflies.

Clancy's Rustic (Platyperigea kadenii)

Oak Rustic (Dryobota labecula)

I must confess that the Oleander Hawk-moth record is not my own; I am only the Determiner (I identified the moth for the person who first reported the sighting). It is included in the list because I curated the record on behalf of the staff at Newhaven Fort and passed the specimen, which was found dead after several days at rest on a wall, to the Booth Museum of Natural History in Brighton. Not included in the list is a second Oleander, which was seen in Seaford in October 2016. Again, I determined the record but this time I put the recorder in touch with the County Recorder.

Two other hawk-moth species were seen during the period, the Convolvulus (Agrius convolvuli) and Hummingbird Hawk-moth. The latter, an impressive day-flyer and favourite of many people, has been seen in disappointingly small numbers each year, but one of the brace seen in 2015 was fascinatingly an overwintering adult which I saw in a vacant house away from the coast in Lewes. The Convolvulus Hawk had never been recorded at home before 2015, but it has been seen during the past two years.

Numbers will continue to surprise and delight each year and this is one of the pleasures and privileges of recording moths by the coast.

Vestal (Rhodometra sacraria)

Butterflies and moths seen in Newhaven during 2016

Each year I run a moth trap at home in the garden (on 209 nights in 2016) and make fortnightly surveys of butterflies and moths at Newhaven's Castle Hill Local Nature Reserve (CHLNR) as part of a shared weekly transect walk. In addition to this I make two surveys of overwintering insects in the Newhaven Fort tunnels, which are adjacent to CHLNR and do a bit of other fieldwork around the town and further afield in Sussex. With all my 2016 data given the green light by the County Recorder, I can now share what I saw.

I've added a list below of the species seen in 2016 in order of abundance. The overall total of c.27,500 butterflies and moths (540-odd species) seen is more or less the same as in 2015, but well below the c.38,500 seen in 2014. The total last year was what it was only due to a massive immigration of Diamond-back Moths (Plutella xylostella) at the end of May and into June, during which I recorded nearly 6200 and saw many, many more. For twelve consecutive nights from 31st May until 10th June the total number of xylostella visiting my trap was in three figures on all but one night (8th), when I had 95. They reached a peak on 4th June, when I counted 1740 in my trap - that's 1740 tiny little moths not more than 6-7mm in body length. It was a good year for other migrant species; the Silver Y (Autographa gamma) made headlines when one landed on Ronaldo's face (#mothonface) and, along with Rusty-dot Pearl (Udea ferrugalis) and Rush Veneer (Nomophila noctuella), all had significantly better years than any of the previous decade or more.

The rest of the data - well, much of it - makes less impressive reading. There were a few high points, however, including records of nineteen nationally scarce species including a beautiful Rosy Wave, a Plumed Fan-foot in the garden, a Portland Ribbon Wave elsewhere in Newhaven, and good numbers of a few species which are gaining a foothold in the area - species like Jersey Tiger and Evergestis limbata, the Dark Bordered Pearl. Several inaugural species records boosted my life list to 856 species and, after six years of recording, my garden list to 663.

A record from 2015 of Cnephasia communana (Coast Shade) also came to light as being the first East Sussex record made for 110 years.

Further afield, excellent numbers of Duke of Burgundy were seen at Heyshott Down near Midhurst and another tiny moth, Ectoedemia heringella, which makes contorted mines on the leaves of evergreen oak (Quercus ilex), and with virtually no previous records in Sussex, was found virtually everywhere that evergreen oaks were found in more than fifty 1km OS grid squares.

The depressing news was that, although numbers of many other species were OK, many more were below average, probably having succumbed to unseasonably warm weather last winter. It is hoped that the frosts of this winter so far will help many species overwintering as larvae or pupae to survive and prosper in 2017.