Saturday, 13 September 2014

Faded beauty

The warmth of the late summer sun is sufficient to stir the last of the season’s butterflies on these east coast dune systems. While a single common blue stands out at a distance against the sandy brown vegetation, the better camouflaged graylings – of which there are many – are not evident until they rise from beneath my feet. Each of the graylings flutters away to settle just a few feet ahead. As they lands so each turns its body, angling its now folded wings at 90 degrees to the sun and exposing the wing and the length of the body to the warming rays. In order to remain active a grayling needs to maintain its body temperature at about 32 degrees Celsius, hence the basking behaviour being so evident at this time of the year.

Without exception all of the graylings I encounter look rather tatty, the wing edges notched and broken, and the wing colouring faded through the loss of covering scales. To be fair, this is not a butterfly for those seeking something bright and colourful; it is a butterfly for those who appreciate the way in which it blends into the dry, dusty habitats within which it lives. The grayling is an unobtrusive butterfly, the females particularly secretive and both sexes rarely observed to nectar on late season flowers. I have heard it said that the adult grayling doesn’t feed but this isn’t true; the adults take nectar very early in the morning and again in late afternoon, outside the hours when most watchers are out looking for butterflies.

The species used to be common on the sandy soils of the Brecks but it has become increasingly rare inland and the best of our colonies are to be found on the dunes at Winterton and Holkham. More widely, the grayling has been lost from many former haunts. It once occupied certain chalk downland sites, where the turf was kept very short, or even scraped bare, by rabbits. Myxomatosis did for the rabbits and, by association, the butterflies. The colony at Winterton, the one I am visiting today, seems to have had a good season, with plenty of individuals evident. Let’s hope that its success continues for many more summers.

Friday, 12 September 2014

The gathering

The walk home has a certain poignancy this evening. Above the riverside limes are swallows and house martins, a gathering of individuals feeding up before departing south. The chattering calls imply a sense of nervous anticipation and emphasise that these evenings will soon slip towards a silence that is broken only by the solitary robin, now delivering his winter song. Only a few brief weeks ago the evening skies rattled with the screech of swifts, their boisterous parties skimming the rooftops and delivering sweeping curves of noise. How quiet it will seem when the last of our summer migrants has gone.

While most migrant birds have to break their journey south to refuel at favoured stopover sites, the aerial-feeding swallows and martins have the option to feed on the wing as they go. In reality, however, even these birds must break their journeys, searching out sites and habitats rich in flying insects. The birds are feeding over the river this evening because there are good numbers of flies and other insects for them to pluck from the air. The same thing was happening the other night at a friend’s stable, the insects associated with the horses and muck providing rich pickings.

It is at this time of the year that we also see swallows and martins gathering on telegraph wires or fence lines. Others may be seen at favoured roost sites, typically situated over water and within a well-established reed bed. The numbers of birds using these sites often builds up over several nights, although the roost may suddenly break up in response to the unwelcome attentions of the local sparrowhawk or passing hobby, attracted to the roost by the pickings on offer. While the sparrowhawk will remain, the hobby may well follow the martins and swallows, harassing them at other roost sites on the long journey south.

I cast my eyes upward each evening as I wander along the river, seeking out these passing migrants. Just occasionally a late swift joins them, silently feeding alongside and also stocking up reserves for the journey ahead. Some of the swallows may winter as far south as South Africa, the swifts a little further north but where the martins go is a mystery still to be answered.

Thursday, 11 September 2014

The root of the problem

While scanning the ground the other morning my attention was caught by a large black weevil, lumbering slowly across the sandy substrate. Thickset, and with a broad nose, it reminded me of the vine weevils that I sometimes encounter in the garden at home. It didn’t look quite ‘right’ for a vine weevil – and I was on stretch of sand dune rather than in a garden – so I popped it in a pot to take a closer look. There was no question that this was one of the broad-nosed weevils, belonging to the family curculionidae; the question was, which one?

The weevils are well represented within the UK, with several hundred species on the latest checklist, and they come in various colours, sizes and shapes. These, however, are based around a common body plan that is characterised by an elongated ‘snout’ – the rostrum – which projects from the front of the head and ends with modified mouthparts. Most weevils use these mouthparts to cut into plant tissue, providing access to the site in which the eggs will be laid. The resulting larvae feed inside the plant on its tissue and it is the diversity of plant species available to the weevils that may help to explain the diversity of species seen within the weevil family itself.

The broad-nosed weevils are, therefore, unusual in not using their modified mouthparts to access the internal tissues of plants for egg laying; it is also why they have a broad rather than narrow rostrum. Instead, they lay their eggs on or near the soil surface and the resulting larvae feed on roots or root nodules without penetrating the plant itself. The resulting damage is still sufficient to see many of the broad-nosed weevils listed as significant plant pests, as the demise of a favourite pot plant to vine weevil larvae quickly demonstrates. The adult vine weevils may also cause damage to the plant, leaving characteristic semicircular feeding notches on the edge of the plant’s leaves.

Putting aside their economic impacts in the worlds of horticulture and agriculture, weevils are rather smart creatures. This particular individual has still got me puzzled, however, and it will be a case of taking it home and looking at it under the microscope to determine its identity. 

Wednesday, 10 September 2014

A cultural history

I spent Saturday participating in a workshop on the cultural history of birds, held at Castle Museum as part of a wider exhibition based around the subject. My own contribution centred on our relationships with owls, a topic that has been at the centre of a book project that I completed last year. Owls illustrate the many different ways in which we interact with birds through our culture and beliefs. They are also familiar and easily recognised, making them an engaging topic for the would-be researcher.

The cultural roles of owls may vary between societies, both across continents and over time, and it has been interesting to chart our changing relationships with them over the course of human history. Some of the earliest evidence of a cultural relationship with owls can be found in the bone fragments of snowy owls recovered from archaeological digs at cave sites dating back many thousands of years. These western European cave sites, which were inhabited by Late Magdalénian hunter-gatherers, contain the bone remains of many different bird species. Many of the bones show butchering marks, underlining the use of birds like bustards, ducks and geese for food. The presence of owl bones is surprising, however, because they carry little meat and are unlikely to have been used for food. Instead, the pattern of the butchering marks indicates a different use. The owls were being butchered for their feathers which, not being waterproof, are likely to have been harvested for a symbolic rather than practical use. We know from more recent cultures that bird skins and plumage may be used for ceremonial dress.

Owls have continued to have a symbolic role down through the centuries. To the Romans a calling owl foretold an approaching death but the Athenians saw the owl as a good omen, indicating the presence of the goddess after which the city-state of Athens was named. English literature makes frequent reference to owls, the birds often introduced to add dramatic effect. It is the owl’s association with the dark of night and with remote places than bring with it the hint of fear. Today, however, as our understanding of their lives has increased, so we are rightly less fearful of these beautiful birds.

Tuesday, 9 September 2014

On the move

There is a bit more wind than I had expected from the forecast but at least there is some warmth in the sun’s rays this morning. It is good to be on the east coast, with sand beneath my feet and some coastal bushes and scrubby cover to search for migrant birds. Over recent days there have been a good few migrants here, including a number that no longer breed in the county but merely pass through on passage. There’s a chance of a vagrant warbler or perhaps a passing shrike. Out on the short-turf of the now vegetated dunes there is even an outside chance of a wryneck.

Today, however, fails to turn up anything rare – not that it really matters. I am not here to tick off something new or to add some rarity to a list. I am here, in this beautiful place, to watch birds and immerse myself within the landscape. What I like about this particular stretch of coast is that there is plenty of scrubby elder cover and a great scramble of bramble and bindweed, all of which provide feeding opportunities for birds and insects alike. Such patches require patient watching because those birds that are present can remain out of sight for long periods. The gentle pebble-tapping alarm call of blackcap reveals the bird’s presence long before it emerges from the bramble in which it has been sat, agitated by the passing dog-walkers.

Over the course of a couple of hours working a few dozen metres of low and crumbling cliff, I am treated to whitethroat, chiffchaff, willow warbler and pied flycatcher; migrants one and all, journeying south. Overhead, the chattering calls of swallow and martin signal other birds on the move, while a few dragonflies patrol lower down, the buzz of their wings catching my attention as the occasional individual steers close to my head and away. Large white butterflies dance around the bramble alongside smaller numbers of comma and red admiral, the latter so beautifully marked that they cannot have been on the wing that long. There is a real sense of movement and it is truly energising to see the ways in which this little stretch of coast is being used.

Monday, 8 September 2014

A hint of autumn

There is a slight chill to the air this morning and already the rank grass by the river is turning brown, signs perhaps that summer is nearing her end. The grass, no longer plump and green with life, looks scruffy, with flowering stalks bent at sharp-angled kinks that bear testament to the lack of life within. The sward itself still reverberates with the sound of a maturing insect community, as bush-crickets reel and grasshoppers chirp.

Rising above the knee-high grasses stand the even taller spires of goldenrod; not the native Solidago virgaurea but the introduced Canadian goldenrod Solidago canadensis, which was first recorded in the wild in 1888 and which has since become widespread. Our native species is now a scarce plant in Norfolk, restricted to a number of moist grassland and woodland edge sites, while its introduced cousin runs rampant on disturbed ground and roadside verge. Like many other established non-natives, Canadian goldenrod is a plant that has successfully jumped the garden wall. Late flowering, it adds some colour to a palette that is shifting from fecund blues and greens towards dry browns and harvest golds. Small flies, evident on the golden yellow flower heads, suggest that the plant may at least be providing some nectar for late season insects.

Many of the grasshoppers and crickets share the colour palette of the changing sward. Each is well camouflaged and it takes a careful eye to pick the grasshoppers out from the stems on which they are perched. Here and there are the larger forms of roesel’s bush-cricket, their tough exoskeletons deeply polished with rich browns and a swipe of cream that edges the side of the pronotum. Despite their camouflage, these engaging insects remain wary, quick to halt their song when you approach and quicker still to dive deeper into the sward when you lean in for a closer look.

I always look forward to seeing and hearing these grasshoppers and crickets, creatures whose nymphs I have encountered throughout the summer now in their adult form and performing a last serenade to the long days of summer. There is something poignant in this marking of the changing seasons and it seems fitting that it is they, rather than singing birds, that proclaim this change.