Sunday, 5 February 2017

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)

Friday, 3 February 2017

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.


Waking the apple tree

A wassail at Newhaven's Castle Hill Local Nature Reserve

Wassail! Norse (Wæs þu hæl) meaning "be thou hale", "be in good health".


On Saturday 7th January we held a wassail around an apple tree on the nature reserve. The Earthquake Drummers led a procession of forty people, their drums lit with colourful lights that made the ground glow as they scared away any dark spirits hanging around in the gathering dark. We formed a circle around the apple tree, which we found amidst a thicket of scrub a few years ago, thrashed the tree with hazel whips to wake it up, blessed it on the command of the Wassail Queen with toast dunked in apple punch, and chanted a wassail verse before withdrawing to the fire for some spiced apple punch and wassail cakes. It was chaotic, mysterious, noisy, smoky and wonderful fun.

When I began to research wassailing I thought we were going to resurrect a forgotten ancient seasonal rite. But wassailing is alive and well and becoming popular again. It's practised on many occasions throughout the year. Like Rough Music, the Wassail has origins that have become dimmed in the depths of time. Pagan, Roman, maybe older, wassailing evolved over the centuries from what was likely to have been a serious sacrificial ritual, a ritual which helped to cultivate confidence in a good harvest at the end of the growing year, into an excuse for a cider-steeped social from one orchard or farm or garth to the next.

Twelfth Night is the traditional wassailing time of year, but there are plenty of examples elsewhere on the calendar; there are echoes of the wassail on Halloween, Bonfire Night (Penny for the Guy) and carolling (God Rest Ye Merry Gentlemen goes to the same tune as many wassailing songs). It is fascinating how time and belief blurs the edges of things, borrows from one and transforms into another. How comforting it is to us humans to join together and make noise and light at the darkest times of year. I think we'll do it again.

A-wassail, a-wassail throughout our town,
Our bread it is white and our ale it is brown.
Our wassail is made of the good ale and cake,
Some nutmeg and ginger, the best we could make.

Our wassail is made of the elderberry bough,
And so my good neighbours, we'll drink unto thou,
Besides all on earth, you'll have apples in store,
Pray let us come in for it's cold by the door.

A-wassail, a-wassail throughout our town,
Our bread it is white and our ale it is brown.
Our wassail is made of the good ale and cake,
Some nutmeg and ginger, the best we could make.

We hope that your apple trees prosper and bear
So that we may have cider when we call next year
And where you have one barrel we hope you'll have ten
So that we may have cider when we call again.

A-wassail, a-wassail throughout our town,
Our bread it is white and our ale it is brown.
Our bowl it is made from the elderberry tree
With our wassailing bowl we'll drink unto thee. 

All photographs courtesy of Peter Varnham.