Early June at Newhaven's Castle Hill LNR: continental visitors arrive

Week 10 of the 2016 transect-walking season

 

Butterfly numbers were again lower than expected with only seven species seen during the walk. The weather during the walk was warm and sunny with only light winds, but this was the first day in a while that the weather was not cool, cloudy and windy. Despite the tendency to think that numbers are poor, upon comparison with most other years numbers are about average - and one species, the Green Hairstreak (Callophrys rubi) has already had its best year to date. Eighteen butterfly species have been recorded so far during 2016.

Diamond-back Moth (Plutella xylostella)

Two overseas species spiced up proceedings: the tiny Diamond-back Moth (Plutella xylostella) and the much larger - and much more noticeable - Painted Lady (Vanessa cardui). The latter was seen flying in off the sea in a northerly direction and these are possibly the vanguard of a greater immigration which may occur over the coming days. These are a strong, unmistakeable insect and there is always a hope that the event of 2008 will be repeated, when many, many millions of these butterflies piggybacked across three generations from the African Atlas Mountains into the UK and as far north even as the Arctic Circle, before their offspring made the return journey back south at the end of their season. 

The Diamond-back Moth is in the midst of a similar immigration event, which hit Newhaven on 30th May, but apparently from the east rather than from southerly climes. I have recorded more than ten thousand of these moths in Newhaven during the past week and I saw an additional 400 - well, 398 - during this walk. Many of these were nestled amongst hoary cress and kale along the cliff bottom and their caterpillars will feed on these and other plants of the cabbage family during the summer. There were without doubt many thousands more than the 400 that I counted, but transect-walking rules are not to be broken, so I counted only what flew up before me as I stepped along the route! I have written a separate report about the Diamond-back Moths which provides more information about this tiny species and the current immigration event.

Large Skipper (Ochlodes faunus)

Whilst these and other exotic species add colour to the nature reserve, we are inevitably more interested in the native species which breed each year at Castle Hill. Numbers fluctuate annually, in response to many variable and confounding factors, and not least the weather. These species have evolved to take the knocks and then make hay when conditions are more favourable. This year is proving to be more or less average when compared with some previous years. It was pleasing to see the emergence of the Large Skippers (Ochlodes faunus), albeit in only small numbers, but these feisty little butterflies, which lay their eggs on Cocksfoot grass, should increase in number during the next few weeks. Common Blue (Polyommatus icarus) numbers are increasing by the week and the first brood should peak in the next two or three weeks, as should the day-flying moths the Mother Shipton (Euclidia mi) and Burnet Companion (Euclidia glyphica), which can be found amongst herbaceous areas along the tops of the cliffs.

Earlier in the year I made a chance observation of a Raven raiding the Barrow Head cliff face hollows which are used as nest holes by a small group of Jackdaws and feral pigeons. The Jacks were perturbed and apparently helpless on that occasion as the Raven leered menacingly into each hole, but there was nothing to steal away at the time (egg-laying time was still in the future) and it flew off empty-handed. I witnessed a repeat raid today, probably by the same Raven. The response of the Jacks could not have been more different: whereas they previously appeared to yield helplessly to their preponderant corvine cousin, today they were a tight fighting force. Arranged in formation they swooped in turn, five Jacks deep, to mob their attacker, they swarmed around, jostled, grappled, set upon, overran and comprehensively saw it off. Within the space of thirty seconds the egg thief was utterly routed. It was spectacular stuff! The Jacks had a most valuable resource to lose this time in their chicks, which must now be very close to fledging. I think this is an example of the concept in the study of behavioural ecology known as the incumbency advantage.

Krebs & Davies (1993) eloquently explained at length how an incumbent (or owner of a resource) has an advantage over a challenger because the incumbent knows or understands the resource at stake, whereas the rival does not possess such detailed knowledge. I am not a behavioural ecologist, but I believe the battle over the Jackdaw chicks (the resource) was an example of this. The investment by the several adults and the bonds with the chicks resulted in a much greater challenge to the Raven than when their nest holes were empty. The hypothesis of the incumbent advantage is that the owner will fight more strongly than the less certain challenger and almost always win. Also, they have more to lose than the predator has to gain. The stakes vary and there are plenty of examples in nature when the predator wins the prey, but I was stunned and mightily impressed by the ferocity of the parent birds on this occasion.

The reserve is easing itself into the summer season now. Grasses are shooting skywards and flowering, along with Thrift and the Common Blue's food-plant Bird's-foot Trefoil on and above the cliff faces. There are the usual concerns about humans' conflicting interests and multiple uses of the nature reserve, but I am not going to bore the reader with a personal diatribe until I have taken the time to convey my feelings - my disgust even - in a more positive light.

The full list for Week 10 (24 species)

Butterflies (7 species) Large Skipper (Ochlodes sylvanus)  3
Small White (Pieris rapae)  1
Green-veined White (Pieris napi)  1
Speckled Wood (Pararge aegeria)  2
Small Heath (Coenonympha pamphilus)  1
Painted Lady (Vanessa cardui)  9
Common Blue (Polyommatus icarus) 12
Moths (17 species) Diamond-back Moth (Plutella xylostella)  398
Common Tubic (Alabonia geoffrella)  1
Light Brown Apple Moth (Epiphyas postvittana) 1
Common Marble (Celypha lacunana)  3
Plum Tortrix (Hedya pruniana)  5
Knapweed Bell (Epiblema cirsiana)  1
Regal Piercer (Pammene regiana)  1 – first site record
Grey Gorse Piericer (Cydia ulicetana)  15
Lead-coloured Drill (Dichrorampha plumbana)  1
Garden Grass-veneer (Chrysoteuchia culmella)  1
Meadow Grey (Scoparia pyralella)  1
Little Grey (Dipleurina lacustrata)  2
Lackey (Malacosoma neustria)  1
Yellow Belle (Semiaspilates ochrearia)  1
Angle Shades (Phlogophora meticulosa)  1
Mother Shipton (Callistege mi)  1
Burnet Companion (Euclidia glyphica) 4
Other highlights Grove or Brown-lipped Snail (Cepaea nemoralis)  1 – not previously found at CHLNR
22-spot Ladybird (Psyllobora vigintiduopunctata)  1
Dock Bug (Coreus marginatus)  7
Green Shield-bug (Palomena prasina)  1

Common Tubic (Alabonia geoffrella)

Garden Grass-veneer (Chrysoteuchia culmella)

Early April at Barrow Head

Transect walking season, weeks one and two

It is the second week in April. My good friend David Harris and I have started our annual season of  transect walks around Newhaven's Castle Hill Local Nature Reserve. We will share alternate weeks between now and the end of October, or whichever time of year that there are too few butterflies on the wing to make the walk worthwhile. This is the sixth year that the transect has been walked and it has become a staple of my wildlife year. It is sometimes a tough commitment in high summer, when all the daily demands of life are queuing up impatiently asking for attention, but the transect walk is always a joyous few hours' escape from everything other than what can be seen before you.

David has walked week one; week two is my turn (David odd; Steven even). In week one only a single butterfly was seen: a Small Tortoiseshell (Aglais urticae) on the clifftop at the extreme west of the nature reserve. We have never had a quieter start to the season.

To compensate for the lack of butterflies and moths, David did make an excellent sighting of the Forget-me-not Shieldbug  (Sehirus luctuosus), also along the clifftop but just to the east of the headland known as Barrow Head. This is not a rare insect, but it is not common either and it's a new species added to our site list. It's food-plants (Forget-me-not or Myosotis species within the Borage family) can be found in quite a few places around the reserve and include Early (Myosotis ramosissima) and Field Forget-me-not (M. arvensis), which are just coming into bloom now, as well as the later flowering species Wood (M. sylvatica)  and Changing Forget-me-not (M. discolor). If luck is with you, you might be fortunate enough to see the small black bug crawling on the ground around the plant or perhaps basking on a leaf.

I have just completed the week two walk around Castle Hill. I am out early because the early morning sun is forecast to be replaced with cloud from late morning onwards. I have seen only one butterfly: a Peacock (Aglais io), on the sheltered glade on the north slope of the reserve. Other insects of interest seen included quite a few Dark-edged Bee-flies (Bombylius major) and an extraordinary number of Buff-tailed Bumblebees (Bombus terrestris) - several hundreds or more all basking in the sun, nestled and half enveloped in grass everywhere along the transect route. It is as though all the bees have been placed under a soporific spell.

As I return to my car, which is parked beneath Barrow Head, I am distracted by an attempted robbery: a lone Raven is visiting each of the many Jackdaw-hollows in the chalk along Barrow Head in search of Jackdaw eggs, like a taxman making house-calls. The Jacks are brave and mob the intruder as it moves systematically from one hole to the next. The Raven visits each hollow not with a short hop but with an exaggerated flycatcher-like loop away from the cliff and back again, tracing a teardrop in the air.

These are both Corvid species, but they are the largest and the smallest and the difference in size is startling. Their evolutionary close kin-ship stands for nothing. The Raven goes calmly about its business and appears to be indifferent to the smaller Jacks as they cartwheel through the air, but the hollows are all empty. It seems the Jacks are still nest-building and have not yet laid their clutch. The Raven perches on the ledge of each, looks monstrously within, pauses for a moment and loops back into the air. With all the house-calls made, the Raven moves away penniless in an eastward direction and the drama is over.

A slab of early morning cloud has drifted off to the east and the spring sun warms my back, while a chilly breeze frisks me from the west, chilly enough to usurp any comfort offered by the sun. As the Jackdaws and Feral Pigeons settle, I climb the slump past them and past Barrow Head on its east side towards a flush of golden flowers which have caught my attention and I find myself suddenly out of the influence of the breeze. Here, it is another day; a hot, calm morning in summer. The heat of the sunlight uninhibited by the breeze is astonishing.

Water-pepper - I think

The flower is Lesser Celandine (Ranunculus ficaria). The starburst flowers open only in sunlight, forming a mirror-mat of gold amidst a nest of heart-shaped green glossy leaves. It is a welcome sight, doubly so because they are the first I have seen on the ground we cleared a few weeks before when we were cutting brambles. It might have grown amongst the thorns in previous years, but it could be a pioneer. This flower, for all its early season beauty, is actually an invasive pest which is blooming amongst the grass in most areas across the reserve. A few steps away is a seasonal pool with what appears to be leaves of Water-pepper (Persicaria hydropiper) reaching up above the surface. It is a plant of winter-wet places. In summer its tresses of pink flowers droop in sorrow towards the parched ground.

Lesser Celandine (Ranunculus ficaria) - growing where recently bramble dominated

As I descend away from the splash of gold and skirt along the base of the cliff a movement to the right catches my eye and I see a basking Adder (Vipera berus) slide towards a clump of long grass with a small hole at its side. As I slowly crouch towards it and rest stone-still, the snake pauses and I am granted a view of the black arrowhead behind its red eyes.

Adders emerge from their underground hibernacula - often a mouse-hole they entered in October-time - at any time from late March or when daytime temperatures climb into double figures. Early mornings and late afternoons are the best times to search for them, when they bask in a sheltered spot, such as this, flattening their bodies against the warm earth, soaking up the sun's energy. This is an essential habit which aids hunting and digestion, especially early and late in the season. The immature male Adder before me will spend the next few weeks feeding mainly on mice or small reptiles such as lizards and slow worms. He'll take all the sun he can find.

This Adder might be the same individual we observed last year. He is not fully grown and I estimate that he is somewhere between two and three years old. Maturity is not reached until four or five years. Adders are fairly slow-growing snakes. He is possibly not mature enough to engage in the violent mating rite sometimes called the dance of the adders, which occurs in April or May. This is a wrestling match fought between males, in which no use of the fangs is made, and in which the winner may mate entwined with a female in a tangle with up to several other males.

Vipera berus - a basking female Adder

Adders are not the indiscriminate biters that some people hold them to be. They are misunderstood and vulnerable, unnecessarily persecuted by humans and predated upon by a number of animals including hedgehogs, birds of prey and crows - including the Jackdaws around the corner of this headland. Their venom is precious to them and they bite only if they are forced to defend. I have given this snake no reason to be fearful and he has paused and rewarded my cautious approach with the gift of a close observation. I back away and leave him to the sun.

The Jackdaws wheel and chatter above me and I return to my car, leaving the birds, bees, Adders and flowers to enjoy the sheltered sunlight.

Secrets of a small rookery, part three: Crow Culture

Wheatfield with crows by Vincent van Gogh (1890), oil on canvas

What is a crow to you, reader? The answer will vary depending on who you are, where you live and the ways in which - and the extent to which - you connect with your environment.

To many people, crows are a noisy, messy, annoying family of birds with unpleasant voices who attack bins and rubbish sacks, steal songbird chicks from nests, steal farmers' crops and generally cause a nuisance. To others they are intelligent creatures, innovative problem-solvers - fascinating to observe and a source of immense pleasure. I am firmly rooted in the latter camp.

In about 1995, while walking along the Ouse riverbank between Newhaven and Piddinghoe in East Sussex, I witnessed a group of several Carrion Crows manoeuvring a square of plywood, which looked like an old drawer-base that had been washed along the river and stranded on the high tide line. One crow wrestled the square of wood down the riverbank and into the water, where it floated. Each crow in turn then flew into the air and attempted to land on the floating wood, not very successfully, and suggesting an appearance of novice surfers, but obviously able to take an idea and put it into practise. This level of enquiry on the part of the crows was remarkable to observe. Whether they were playing or attempting to gain some advantage, perhaps by using the floating wood as a fishing platform, I could not speculate about, but it convinced me that crows are clever birds.

Soler & Møller (1990) demonstrated that Magpies (Pica pica) learnt to detect Great-spotted Cuckoo (Clamator glandarius) eggs when their nests had been parasitised in areas where the two species had coexisted for some time. The ability to detect these eggs was reduced in areas where coexistence was more recent and, where their ranges did not overlap at all, there was no recognition. Magpies had developed the ability to recognise cuckoo eggs through learning experiences and had tweaked their behaviour accordingly. Other victims of brood-parasites, such Reed Warblers (Acrocephalus scirpaceus) and Dunnocks (Prunella modularis), have shown no such recognition of Common Cuckoo (Cuculus canorus) eggs. The New Caledonian Crow (Corvus moneduloides) is a well-documented problem-solver, tool-maker and tool-user (Hunt, 1996). Crows are clever birds and their intelligence has impressed and captured the imagination of the humans in their midst.

To many human cultures crow species are a defining cultural reference: gods or messengers of gods, spiritual beings who may deliver the souls of the dead to the afterlife. They are emblematic, their image having been used in aboriginal art including cave paintings and aboriginal names and costumes, heraldic coats of arms, place names (Rookery Hill, Rookery Way and The Rookery are all about a mile away, as the crow flies, from where these words are being written) and in numerous other creative works. We have exploited crows in our culture and crows have adapted to exploit us too. This entwined relationship can be termed cultural coevolution.

Ravens scavenging a wolf kill-site carcass

Here is an example of cultural coevolution: the automobile is one of the defining images of the American Dream. Perhaps there is an inevitability, therefore, that the American Crow (Corvus brachyrhyncos) has adapted its own culture in response to road vehicles. Traditionally, Ravens (Corvus corax), Magpies (Pica pica) and other corvid species adapted and evolved to scavenge the carcasses of hunted animals which they locate by flying and searching across the landscape, perhaps following packs of wolves or humans to a kill-site. Roadkill could be considered to provide the same opportunity, particularly in areas where kill-sites are less common now than they were in the past, so it is not much of a cultural shift on the American Crow's part to follow roads, which cut like rivers through the landscape, searching for dead deer, rabbit or birds. American Crows have also been observed picking dead insects from the fenders of stationary cars. These behaviours should still be considered as a cultural response; they have been observed in North America (Marzluff & Angell, 2005), but probably also occur wherever crows and humans with cars coexist. In Japan in 1975, Carrion Crows (Corvus corone) were observed at a driving school placing shelled walnuts before the wheels of parked cars so that they would be cracked open as the cars drove over them and away. This behaviour has been adopted by observant crows and has since spread some miles along the Hirose River region (Nihei & Higuchi, 2001).

Further reading provides a wealth of examples which demonstrate the effect that crows have had on European culture, and particularly so on our languages, which will be the subject of part five of this corvine compendium.

I think the relationship between crows and humans, whether it is welcomed, tolerated or despised, dates all the way back through human history, back beyond the 150,000 or so years that Homo sapiens has walked across the world, even back beyond the seven million years since our evolutionary trajectory branched away from our closest extant relatives, Bonobos and Chimpanzees. Crows have been on the wing all this time - they evolved (I think) in the Eocene Epoch about 50 million years ago, although the species we share the world with today are more recent. At the end of the last ice age ten thousand years ago, Hunter-gatherers would doubtless have been in close contact with Ravens, who followed or possibly even led humans along the migration routes towards the great herds of ungulates, where we might have revered the birds, tolerated them or chased them off from a kill. As farming practises spread from the Middle-east westwards across Europe and into Britain about six or seven thousand years ago, we would have put down roots and found ourselves closer to other crow species such as Rooks and Jackdaws, who colonised the fringes of the land cleared by our ancestors and who plundered the insect pests which devoured our ancestor's crops and then helped themselves to the same crops as they ripened.

Four seeds in a hole,

One for the Rook, one for the Crow,

One to rot and one to grow.

During the past few thousand years of civilisation and warfare, battlefields strewn with dead soldiers would have been a happy hunting ground for Ravens, Carrion Crows and Magpies. Survivors who witnessed the battlefield-fallen being pecked and torn apart in a corvine feeding frenzy could be forgiven for holding a fear or awe of those birds whenever their paths crossed.

Gallows-crows

The same crows would have perched upon gibbets and gallows and it is easy to imagine them gathering ahead of a public execution - observant and intelligent birds would learn to recognise the signs, the noise of excitable crowds. The black, ravenous birds would understandably have become symbols of judgement, both human and divine judgement.

The crow or raven might have been the influence of the beak-shaped mask worn by plague-doctors in Europe during the 16th and 17th centuries. The costume of a waxed or leather cloak was topped with a mask and beak. The beak was filled with straw and aromatic herbs and oils - all to filter and protect the plague-doctor from miasma (putrid air), which was considered until modern times to be a vector of disease. Even Florence Nightingale is alleged to have believed in misama theory, but the Nightingale is a different bird altogether. The beaked mask of the plague-doctor is still a chilling sight.

We have shaped crows' culture and they have shaped ours. It is no wonder that crows became symbols of fear, death and perdition. It is via this background that crows and crow-culture have become braided into our language.

Plague Doctor costume

References:

Hunt, Gavin R. 1996. Manufacture and use of hook-tools by New Caledonian Crows. Nature 379: 249-25.

Marzluff, John M. and Angell, Tony. 2005. In the Company of Crows and Ravens. Yale University Press: New Haven.

Nihei, Y. and H. Higuchi. 2001. When and where did crows learn to use automobiles as nutcrackers? Tohoku Psychologica Folia 60: 93-97. 

Soler, M. & Møller, A.P. 1990. Duration of sympatry and coevolution between the great spotted cuckoo and its magpie host. Nature. 343, 748-750.