Saturday, 12 January 2008

Mink still cling on

Over the years I have seen many a gamekeepers’ gibbet, each one hung with an array of feathered and furred ‘vermin’. The gibbets show that the keeper is doing his job and this function must also be behind the dead mink that are sometimes displayed in prominent positions on the local nature reserve. The reserve covers a series of old gravel workings, now stocked with fish and managed by a local fishing syndicate. The revenue from the fishery pays for a part-time warden and ensures that all-important habitat management work is carried out. It seems to be a decent arrangement and the wildlife clearly benefits.

The fishermen view the introduced mink as a threat to their fishery and so control them if and when they appear. Since mink are also predators of various water birds and other vertebrates, the control also has conservation benefits on the site. It is unsettling, though, to see any creature killed and exhibited like some macabre trophy. Don’t get me wrong; mink control is regarded as being an important part of the conservation work taking place across many of our wetlands, supporting the popular view that the arrival of mink has had a pronounced impact upon prey populations.

Mink were introduced to Britain from North America and bred on fur farms from 1929 onwards. Escapes and deliberate releases quickly led to the establishment of a feral population, which soon became self-sustaining, initially in Devon (during the 1950s) and then elsewhere (from the late 1960s). The species is an opportunistic predator, taking a very wide range of fish, bird, mammal and invertebrate prey, from beetles and earthworms, through to crayfish, small mammals, water birds and even rabbits. That the species has been able to establish itself so successfully within the country, suggests that it has found a vacant niche, something that is reinforced by research demonstrating that there is little or no competition with any of our native mustelids (weasel, stoat or otter). In fact it has even been suggested that the return of otters to an area results in the loss of the mink. That certainly hasn’t happened here in Breckland; even though the otters have returned, the mink are still present and there are plenty of rivers elsewhere in Britain that also still support both species, often on the same stretches. Mink are territorial and fairly easy to trap but the frequent removal of territory-holding individuals tends to lead to an enlargement of home range, meaning that the mink will remain present but at a lower density. This suggests that mink are here to stay and will remain a feature of our rivers and wetlands for many years to come.

Friday, 11 January 2008

The river

I am drawn to the river; this dark, sediment-laden entity that meanders through the valley towards the distant fens. There is something about water, the way in which its character alters with the seasons, its moods a reflection of the wider changes taking place across the landscape. During the dry months of summer it slumbers, moving slowly under the oppressive heat and to the background sound of a thousand waterside flies. Now, in winter, after rain it has acquired a new strength, a swirling deep brown mass of energy that shifts debris, sweeping away the year that went before to start anew with the coming spring.

I am not the only creature drawn to the river today. A grey squirrel crouches on the shallow incline of a muddy bank, its head down drinking from the water. It appears stiff, bow-legged and, at first, it does not see me but then, startled by the sudden realisation of my intrusion, it retreats into the cover of the trees, all the while berating me for my indiscretion. The bankside alders hold small parties of siskins, their soft chattering calls a communal reassurance that all is well with the world. These delightful little finches visit my garden every day at this time of the year but I much prefer to see them here, feeding on the alders and showing off their exquisite dexterity. Like diminutive acrobats they hang from the ends of tiny branches to reach the cones. Further ahead, as I leave the damp woodland behind to emerge onto the old floodplain, the river slides slowly past a fishery. Wrens foraging in the deep sedge rattle at my presence, while a flock of long-tailed tits - a baker’s dozen strong - flitter to and fro across my path. In the past I have seen overwintering chiffchaffs here but not today.

Such is the colour of the water that I cannot see anything below the surface; there is no hint of the chub and roach of summer, yet they must be here. The loss of the submerged dimension only adds to my fascination with the river. There is a world here, just beyond reach, that I cannot see. What creatures move through the murky water? Has one of the local otters slipped past unnoticed or is there a pike hanging motionless just feet away from where I stand? T S Elliot once described a river as being a strong brown god, and I can relate to this allusion. The subtle strength of the river allows it to mould the landscape to its own ends, it supports life and it provides endless fascination to those of us who live within its reach.

Wednesday, 9 January 2008

Overlooked pipit

The water pipit is one of those unobtrusive birds that has, in the past, tended to be overlooked by birdwatchers. The main reason for this was that the water pipit was not recognised as a full species until 1986. Prior to this date it was widely regarded as being a race of the rock pipit, also a local bird within the UK. In fact the relationships between the two species, together with another – the buff-bellied pipit – had been the subject of a great deal of discussion and some controversy. Subtle differences in plumage, behaviour and habitat use hinted that these three pipits were separate species but there was no definitive proof. Fortunately, analyses of mitochondrial DNA sequences have revealed the degree of separation between the three birds and now most authors treat them as distinct species.

Water pipits are scarce winter visitors to Norfolk, with fewer than a hundred birds thought to be present within the county in any given year. They do not breed here but arrive from breeding grounds that are thought to lie in the Pyrenees, the Massif Central, Jura and the Alps. While their cousin the rock pipit is a bird of the rocky coast, the breeding water pipit is a bird of the mountains. The association with water suggested in the name, comes from the habitats used by the species during the winter. Here the bird prefers to feed on areas of lowland wet grassland, brackish lagoons, along river banks and at sewage works, where it takes insects and a small amount of plant material. In such habitats the species may be seen feeding alongside the more familiar meadow pipit.

Finding and identifying water pipits can involve a degree of patience, especially when they are feeding within rough vegetation. Slightly larger than a meadow pipit, they usually (though not always) show dark legs – meadow pipits always have pale legs. The upperparts are grey-brown in winter and lack the olive-green tinge often seen in meadow pipits. The rump and back are unpatterned. Separation from rock pipit is more difficult and the flight calls of the two species are indistinguishable. It is even possible to confuse the flight calls of water and meadow pipits though, to my ear, that of the water pipit is higher in pitch, less resonant and not as short or rich in structure.

Norfolk holds wintering water pipits at a number of regular sites. Perhaps the most dependable are Buckenham Marsh, Hickling and Strumpshaw, though Lakenheath Fen seems to have been well used over recent winters. The water pipits, which arrive here in late October, will remain through into March, when numbers may peak, so why not see if you can spot one.

Tuesday, 8 January 2008

Roe doing well on the fen

The roe is the deer of my youth, frequently observed as I explored an ever-increasing range spread along the Surrey/Sussex border. Each small block of woodland appeared to have its resident pair of roe, which would venture out onto the adjoining pastureland to feed at dawn and dusk, and so the species became something of a talisman for my youthful wanderings.

Here in Norfolk roe are deer that I only see once in a while, replaced by everyday sightings of the diminutive muntjac that have done so well in this part of the county. However, there are occasions and places where I see roe in good numbers. At this time of the year the roe, which as a species tends to avoid the herd instinct, can come together in small groups at sites where the habitat is most favourable to them. The RSPB reserve at Lakenheath Fen is one such site and eight or 10 individuals can be seen if you visit just after dawn. Roe are extremely inquisitive animals and, if feeling secure, will stand and watch you, providing an ideal opportunity to take in their character. On a dull January day the roe will be in their winter coats, brownish grey in colour and made up of long wavy hairs that help provide insulation against the vagaries of the fenland winter. This coat is very different from the sleak fox-brown summer coat that will be grown from April or May but their drab winter tones are well suited to the January landscape. The dark muzzle and white chin are characteristic when the roe is viewed from the front, the dark eyes staring intently at you and the large ears alert to other sounds. Even when viewed from behind the species should be recognisable, the pale rump (white in winter, buff in summer) is oval shaped and lacks any obvious tail (the latter being diagnostic for the species).

Although regarded as a native, the roe population underwent a marked decline such that, by the start of the Eighteenth Century, it was restricted to remnant woodlands across parts of the Scottish Highlands. There was something of a recovery after this period but this only brought the species back into northern England; it is thought that all of the roe in East Anglia derive from animals introduced from elsewhere in Europe.

The small groups at Lakenheath will break up by April, the males establishing breeding territories which they will hold throughout the summer months to secure access to the females, once they come into season. The level of visible activity during daylight hours is also likely to decline as the months progress, so take your chance now to see these wonderful animals.

Monday, 7 January 2008

Butcher bird haunts the heath

The forest can be rather bleak in winter, with little sight or sound of the bird life that abounds during the warmer months of summer. As such, I did not set my expectations very high when I set off to visit the survey square allocated to me for Bird Atlas 2007-11 (, a four year stock take of our breeding and wintering birds. The survey square was dominated by plantation woodland and I knew that unless I stumbled onto a roving flock of tits I would not see that many birds. Still, it needed to be covered and I set off in an optimistic frame of mind, glad to be out on such a fine winter morning.

As I worked my way through the mixed-aged stands of conifers I added small, but increasing, numbers of birds to my field log, collectively amounting to most of the range of species that I had expected to see. Then, completely unexpectedly, I spotted a great grey shrike sat, sentinel-like, in the top of a small birch in a piece of clearfell. This magnificent individual was the first great grey shrike that I had found myself, something which made the sighting all the more special.

Small numbers of these shrikes winter in Britain, favouring open areas with scattered bushes from which they can scan for prey; the second part of its Latin name, ‘excubitor’, means ‘sentinel’ and refers to this habit of utilising prominent perches. The other part of the Latin name, ‘Lanius’, derives from ‘lanio’, which means ‘to tear into pieces’. This is a reference to the bird’s predatory ways and hints at the old country name of butcher bird, applied to this and other shrikes. These birds feed on large insects, small birds and small mammals which, in times of plenty, they impale on thorns or the barbs of barbed-wire fences, just as a butcher would with cuts of meat. Caching prey in this way is an insurance policy in case of tougher times ahead.

Because my visit to the survey square was timed, I could not spend long admiring the shrike and so had to move on. Once the timed recording was complete I returned to the spot where I had seen the bird but it had gone and I failed to turn it up again before having to head home. Some of these wintering shrikes establish winter feeding territories on which they remain over many weeks but others are mobile. This bird may have been one of these or it may simply have found this part of the forest unsatisfactory. Two others have been seen locally in recent days, could one of these be the bird that I had chanced upon?