Thursday, 31 August 2017

Late August at Castle Hill LNR, Newhaven


I did the week 22 walk on Sunday 27th in what for Castle Hill was uncharacteristically calm weather. This made for good butterfly conditions along the clifftops and there was much activity for the time of year. I counted 366 butterflies and moths of 13 and 12 species respectively. This is not a bad haul, but is lower than the same week in the previous two years, when over 400 were counted. Week 22 has usually been the final week of abundant activity at Castle Hill, so we might find a drop in numbers next week.
Straw Conch (Cochylimorpha straminea)

I don't want to get too carried away with excitement, but there has been something special happening this year for the Small Heath butterfly. I have been recording more than 130 at Rookery Hill in Bishopstone on some days recently and, on Sunday, I recorded nearly as many Small Heaths in one day (96) as we counted in the six years between 2011 and 2016 (113 in total during this period). Both Dave Harris and the County Lepidoptera Recorder, Colin Pratt, have commented that this butterfly appears to have recovered to its pre-decline 1970 population level. Let's hope it is sustained in the coming years. Isn't it wonderful to have a success story for once when considering the plight of so many other species?!!

Amongst the moths, I recorded our first Straw Conch (Cochylimorpha straminea) in seven years at the reserve and saw more of the Common Grass Veneer (Agriphila tristella) than we've ever counted before in a single day. This moth is having a good season and has been seen in good numbers everywhere recently. This distinctive moth, which has a pale streak running along the length of its wing, flies out of the grass ahead of you when you walk along country paths in the late summer and lands a few metres ahead, parallel with a grass stem.

Purple Loosestrife
Other items of interest include some purple loosestrife found growing by the 'old pond' (Dave tells me this is a new plant species for the reserve list) and some birds including a female Wheatear, two ravens and a sparrowhawk all along the clifftop.

Amongst the photos I've included is a shot of a hazy Seaford Bay. This haze is the infamous cloud that affected people later in the day on the beaches between Birling Gap and Hastings. When the weather is settled and sunny, an accumulation of pollutants such as oxides of nitrogen and other volatile compounds react with UV in strong sunlight to create ozone at low levels. This 'photochemical smog' causes severe irritation to eyes, nose and throat upon exposure. Air quality data measured at the Lullington Heath station on the same day showed a large spike in ozone levels. Thankfully those people at Newhaven's West Beach were not so affected.

Hopefully there will be no such hazards for Dave during week 23.
 
 
 
Low-level ozone at Seaford Head?



Late summer colour in the Wassail Glade at Castle Hill LNR
 
 25 species (13 butterfly, 12 moth); 366 individuals.

Large White (Pieris brassicae) 21
Small White (Pieris rapae) 68
Green-veined White (Pieris napi) 1
Clouded Yellow (Colias croceus) 2
Speckled Wood (Pararge aegeria) 19
Small Heath (Coenonympha pamphilus) 96 – highest numbers ever seen at CHLNR
Meadow Brown (Maniola jurtina) 65
Gatekeeper (Pyronia tithonus) 1
Red Admiral (Vanessa atalanta) 6
Painted Lady (Vanessa cardui) 1
Small Copper (Lycaena phlaeas) 4
Holly Blue (Celastrina argiolus) 2
Common Blue (Polyommatus icarus) 25

Golden Pigmy (Stigmella aurella) leaf-mines on bramble
Bordered Carl (Coptotriche marginea) leaf-mines on bramble
Apple Leaf Miner (Lyonetia clerkella) leaf-mines on apple and cherry
Common Nettle-tap (Anthophila fabriciana) 3
Straw Conch (Cochylimorpha straminea) 2 – first site record since 2010
Straw-barred Pearl (Pyrausta despicata) 10
Rusty-dot Pearl (Udea ferrugalis) 1
Rush Veneer (Nomophila noctuella) 3
Common Grass-veneer (Agriphila tristella) 32 – best numbers ever seen at CHLNR
Common Carpet (Epirrhoe alternata) 1
Vapourer (Orgyia antiqua) 1
Silver Y  (Autographa gamma) 2
 

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
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





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.