Saturday, 14 September 2013

A shifting of our baselines

Read the writings of different generations of naturalists and you will soon discover that each generation has its own perspective on the wildlife and landscapes with which it has grown up. As each generation ages so it begins to look back at the landscapes of more youthful days, highlighting what has been lost and how formerly rich plant and animal communities have become diminished.

What is most interesting about this is how each generation sees things as being ‘better’ for the generation that came before. My generation witnessed the surge of agricultural intensification that came in the 1970s, my father saw the changes that followed the Second World War and his father grew up with an agricultural landscape that depended on horses rather than horse-power. Taking this back over more generations through literature and nature writing, you’ll find John Clare and many others writing about the terrible changes happening to their countryside, a countryside that we would view with envy for its biological richness.

The name given to these different viewpoints is shifting baseline syndrome. This syndrome has its basis in the relatively short duration of our lives and in our inability to appreciate changes happening over longer periods of time. If you are born into a landscape from which red-backed shrikes, wrynecks, beavers or even wolves have been lost then you have no sense that they were ever there and you accept their absence. You might notice and complain about the loss of spotted flycatchers or turtle doves but, once they are gone, the generation that comes after you will fail to register their absence.

Shifting baseline syndrome manifests another problem for conservationists, in that our attempts to re-establish lost species or habitats become blinkered. Habitats that we champion as ‘wild’ today (think of our uplands) are very different from how they would have been if we had not come along in the first place. Our activities, such as the removal of most of our mammalian ‘mega-fauna’ by our ancestors, have had profound impacts on the ecological processes that shape our landscape and its communities. If we are to ‘rewild’ and restore lost habitats then we first need to understand what was really here and why.

Friday, 13 September 2013

Wonderful Wrynecks

This autumn has seen a larger than usual passage of wrynecks, with good numbers of these smart little birds arriving on the coast over a single weekend. Most were seen at traditional sites, like the dunes at Holme and the short turf of Beeston Bump, but a few turned up further inland, including one at the RSPB’s Strumpshaw Fen reserve.

The wryneck is a member of the woodpecker family, a sister species with an ancient and separate lineage from our other woodpeckers. It was once a familiar breeding species in England, with most English counties holding breeding pairs at the end of the Nineteenth Century. Since then the breeding population has evaporated, with numbers dwindling over the following decades and the species lost as a regular breeder. Very occasional breeding attempts are noted today and the wryneck is now best regarded as a passage visitor, passing through on spring and autumn migration. Unusually for a woodpecker the wryneck is a long-distance migrant, with western populations breeding in northern Europe and wintering in sub-Saharan Africa.

Passage wrynecks seem to like the short turf of garden lawns, a consequence of the ant colonies they support. Spending a lot of time on the ground, wrynecks can be tricky to spot because of their vermiculated plumage: a mix of browns, greys and black. Unlike other woodpeckers wrynecks do not use their tail for support when climbing, nor do they hammer at wood with their bill, preferring instead to chisel and lever away material.

The loss of wrynecks from Britain as a breeding species has been linked by some to a decline in ant populations, but it is more likely to be the result of a wider decline in populations over the western European part of the breeding range. Britain is on the margins of this breeding range and any decline in populations elsewhere is likely to have had an impact here. Your best chance of seeing a wryneck is to visit the coast at this time of the year and to seek out areas of short turf – golf courses are ideal. Watch the weather forecast the evening before and look for a run of easterly winds that may push autumn migrants towards our shores.

Thursday, 12 September 2013

A bounty of butterflies

The last few weeks have seen a noticeable upturn in the numbers of butterflies on the wing, with small tortoiseshell perhaps the most abundant of these. After the slow start to the year for many species, the ‘good’ summer that has followed has given our butterfly populations a real boost. The presence of so many small tortoiseshells is particularly welcome given the fortunes of this familiar butterfly over recent years. Numbers, which normally show an increase towards the end of the summer, have been lower lately and comments have been made about the possibility of a longer-term decline.

Small tortoiseshell populations here in Britain are influenced by a number of different factors, one of which is the weather. Periods of hot and dry weather during the caterpillar stage lead to faster growth rates and a larger emergence of adults. However, parasite populations also shape tortoiseshell numbers and the arrival of a new parasite was thought to have increased the pressure on British populations. Until relatively recently, small tortoiseshells were only parasitized by a number of generalist parasitic flies and wasps, parasites that also target other species. The arrival of a new parasitic fly, called Sturmia bella, just over a decade ago was thought to have changed things somewhat – at least over the short term. This species, which is more of a specialist, lays its eggs near to small tortoiseshell caterpillars. These are ingested along with the plant material on which the caterpillars are feeding. The eggs then hatch inside the caterpillar, before the resulting larvae go on to kill it. The larval fly (a white maggot) emerges from the butterfly’s chrysalis and descends to the ground on a silken thread.

Although the arrival of this new parasite may have had some initial effect, evidence from elsewhere suggests that the recent declines in small tortoiseshell populations here are not linked to the parasite but are, instead, the result of a run of poor weather. While a hot and dry summer may boost the numbers of adults seen, summer drought can reduce the availability of nettles (and in particular fresh nettle growth), used as a food plant. It will be fascinating to see how populations fare going into 2014.

Wednesday, 11 September 2013

A great vision

Mention of the Fens conjures up images of a lost landscape, a landscape once dominated by water and rich with wildlife. Today this landscape is one of intensive agriculture and horticulture, the waters tamed by the framework of drainage ditches and pumps that regulate water flow and control water levels. All that remains of this once great fen is a tiny fragment, an echo of that former landscape held in trust as a nature reserve. Even this fragment cannot escape the creeping reach of progress; the waters that flow into the reserve carry with them the polluting waste and excess nutrients from the surrounding farmland, altering the structure of the plant communities within.

There is, as you will no doubt have seen, a creative vision that seeks to re-establish the ‘Great Fen’ over part of its former range. While this too is only a fragment of that lost landscape, it is a larger fragment and one that should, therefore, be more robust to the reach of the intensively-managed landscape beyond its boundaries. I paid my first visit to that vision the other week and saw for myself the scale of the project, both in terms of the area to be ‘reclaimed’ and of the technical challenges that lie ahead. Reversing the effects of decades of agricultural ‘improvement’ will not be easy and there is much that needs to be undone.

The Great Fen project is the first lowland attempt at landscape scale conservation and it is an ambitious project full of challenges, not least raising the many millions of pounds needed to purchase land currently under agriculture. The energy and vision of those working on the project are, however, two fundamental reasons why it will succeed and why it will deliver something that is worthy of being called a ‘great fen’. To see parts of this landscape as they are now, with carrot fields and other crops, and to then see areas that are being transformed into reed beds and pools, underlines what is possible. I shall return to this landscape-scale project again and again over the coming years to watch its progress and, I hope, to see the recreation of a fenland rich in wildlife.

Tuesday, 10 September 2013

Siberian sandpipers put on a show

A somewhat flat start to the day, with high cloud and a hint of autumn chill, found me sat in one of the hides at Cley, scanning the muddy shallows for waders. Along with an occasional godwit, a scatter of lapwing and a few dozen ruff were two small groups of more delicate waders – one numbering four individuals, the other five. These were curlew sandpipers, a species that breeds along the coastal margins of northern Siberia and winters widely, from West Africa to Australasia. It is a passage visitor to our shores, with larger numbers passing through in autumn than in spring.

Curlew sandpipers are, in some respects, similar to dunlin, the latter species providing a useful starting point when attempting identify many a small wader. Slightly larger in size than a dunlin, these curlew sandpipers had a more upright, somewhat elegant, stance that was clearly evident as they fed in the shallows. These were all juvenile birds, with clean white underparts, a smudge of colour on their breasts and nicely marked backs. Later in the morning a good-sized flock of dunlin dropped in and soon the two species were feeding alongside one another, providing the perfect opportunity to underline the differences between the two species. When seen together, the longer, thinner and more curving bill of the curlew sandpiper is clearly apparent, although it is not necessarily a useful identification feature when viewed in isolation.

The numbers of these delightful little birds passing through our shores represents a tiny fraction of the global breeding population and probably derives from those birds nesting at the western end of the breeding range and wintering in south-west Europe and West Africa. Passage numbers, which peak in September, tend to fluctuate from one year to the next, with occasional years when very large numbers pass through. Numbers show some correlation with how successful the breeding season has been but are more strongly influenced by autumn weather conditions. A run of easterlies over Scandinavia and the Baltic during autumn passage, sees more individuals reach our shores, which is good news for us birdwatchers. Most will be seen on the coast, at places like Cley and Titchwell, so now is a good time to go and find them.

Monday, 9 September 2013

A great green chorus

As the car slowed on our approach to the level crossing gates I could hear a sound I recognised. ‘Conehead?’ queried my fellow passenger; ‘great green bush-cricket?’ came my response. ‘Yes, that’s it, shall we take a look?’ At this time of the day the crossing gates would be down for a while and the traffic on this minor road was always minimal. Alongside the road was an expanse of rank grassland, bracken and nettles, an ideal spot for the largest of our British orthoptera (grasshoppers and crickets). Within a couple of minutes I had located an adult male, perched (as they often do) towards the top of a bracken stem. It was a stunning beast.

The great green bush-cricket lives up to its name. At 40-50 mm in length, this is a striking insect. Despite this, the species is often overlooked within its southern range, a range that lies to the south of a line drawn from the Wash to South Wales. In part this is down to its preferred habitat of rank grassland that is moving in succession towards scrub – it’s not a habitat most people inspect too closely. However, the great green bush-cricket’s nocturnal habits probably also have a role to play. The males usually begin to sing from mid-afternoon on sunny days but the main activity happens at night. The females are inactive during daylight hours, spending the time basking. If found, and disturbed, they will climb up the stem on which they have been resting, a behaviour that is uncharacteristic of bush-crickets more generally, which tend to dive into cover at your approach.

These engaging insects are omnivorous, feeding on plant material, aphids, flies, caterpillars and other grasshoppers and crickets. Their habits have been well studied in captivity where, according to the famous French entomologist Henri Fabre, they resemble the English, doting on ‘underdone rump steak seasoned with jam’!  Observations of captive individuals have revealed that the eggs are laid in the soil during summer, passing two or more winters before hatching in a subsequent spring (usually late April or early May). The adults emerge in July, following a number of larval instars, and remain active into October, so now is a good time to look for them.