Sunday, 10 April 2016

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.

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