Saturday, 15 December 2007

'Christmas trees' provide a new home

Several of the conifers growing in our garden when I was young were old Christmas trees, planted out having served their festive purpose. As such, I used to refer to any suitably shaped conifer, regardless of origin, as a Christmas tree. Today, a wide range of conifers are used for Christmas trees and, indeed, for other ornamental purposes. One of these, the leyland cypress, has made the headlines on occasion when neighbours have fallen out of over the size of hedge this tree can achieve. The Leyland cypress was first created as a hybrid, by crossing Monterey and nootka cypress, but it now occurs alongside many other cultivars.

The widespread establishment of these new cypresses has opened up opportunities for a number of different insect species, including several moths. Juniper is our only native member of the cupressaceae (the family of conifers which includes the cypresses) but other members are native to southern Europe and these support a number of moth species not originally found in Britain. However, over the last 60 years several species have established themselves here. The first of these reached us in 1951, when a Dr Blair discovered Blair’s shoulder-knot feeding on a Monterey cypress on the Isle of Wight. By the 1960s this species had reached the mainland and began to spread inland. It now occurs across much of Britain, reaching as far north as Tyneside and southwest Scotland. Blair’s shoulder-knot had been extending its range from the Mediterranean around the Atlantic coast of France and, from there, it was a short hop across the English Channel.

Other species to reach us include the cypress pug and the cypress carpet, arriving in 1955 and 1984 respectively. Although now well-established, both species have failed to penetrate very far north and are restricted to the extreme south of England because they are prone to winter frosts. A number of smaller moths, just a few millimetres in length, have also reached our shores to exploit the new cypress resource. One of these, Argyresthia trifasciata, is a stunning little fellow, with golden wings across which run three white bands. Its caterpillars feed within conifer shoots and the shoot tips soon turn brown, leaving a clear sign that the moth has colonised a tree. Although such species may have been able to extend their European range northwards thanks to global climate change, they could not survive here without the presence of the cypresses. Other species have been assisted by the international trade in conifers, piggy-backing on trees imported from North America. The cypress tip moth that is established around Ipswich almost certainly arrived this way. At least one native species has been reported feeding on cypress and others may follow.

Friday, 14 December 2007

Red in tooth and claw

I am fascinated by predators and our perceptions of them, the way in which people can react so aggressively to the presence of a sparrowhawk in their garden or to the sight of a magpie with a chick in its bill. Many of us seem unable to let nature act out its daily performance without interfering or choosing sides. Anger at the loss of a blue tit to a sparrowhawk is not mirrored when a blue tit predates a caterpillar or a blackbird pulls up and dispatches an earthworm. Why is this? There is no ecological difference between these various acts of predation, so why should we accept one and challenge another? I think that it has a great deal to do with our perceptions and the affinities we establish with certain creatures, while largely ignoring many thousands of others. Examine any list of our favourite animals and the chances are that those at the top of the list will be furred or feathered. Even within birds and mammals, we have our favourites. For example, while magpies are widely disliked for their predation of young birds and eggs, we are delighted to see a great spotted woodpecker, even though it is also a predator of nesting birds. Great spotted woodpeckers regularly break into tit nest boxes, first tapping the box to elicit a response from the nestlings (thus determining that it is occupied) and then drilling in to extract a meal.

It is essential to understand that nature is “red in tooth and claw”; it is cruel and vicious and unsympathetic. We should not impose our moral values onto wild creatures but instead accept that they are following their natural instincts. Accepting predation in all its forms is, I believe, an important step towards reconnecting with the natural world. By imposing our views of what is and is not acceptable we are distancing ourselves, setting ourselves apart in a way that is unhealthy and, potentially, unsustainable.

A failure to understand the ways in which populations of different species interact, through processes like predation, can reinforce misguided views about the nature of predation. I have received no end of letters over the years from people who have been quick to point an accusatory finger at birds of prey, calling for a cull of their numbers to halt the decline in various songbird populations. Yet, there is no scientific evidence to implicate predators in the declines of our songbirds. The evidence that is there supports the hypothesis that it is habitat change (through agricultural intensification and changing woodland management practices) that is the root cause. However, the act of predation unsettles us and it is easy for some to blame avian predators.

Thursday, 13 December 2007

December is a good month to see our smallest duck

There is something rather special about a visit to the North Norfolk coast at this time of the year. The coastal marshes and flooded pastures support huge numbers of wintering wildfowl, and it is quite something to see and hear the feeding flocks of ducks and geese. Such winter visitors include the diminutive teal, our smallest native duck and one of my favourite birds. Its clear, ringing whistle is such a characteristic sound; shorter and with a harder edge than the soft whistles produced by the wigeon alongside which teal are often found. Flocks of at least 1,500 individuals may be seen at Cley, while another Norfolk Wildlife Trust reserve, Hickling Broad, regularly supports up to 3,000 birds. Far smaller numbers of teal occupy waterbodies that are situated well inland. However, I have seen them on the Breckland meres and on smaller pools spread across parts of the southwest of the county.

Although small numbers of teal breed in Norfolk, our wintering population is largely drawn from birds that have bred in Iceland, Scandinavia, the Baltic States and east into Siberia, making Britain an internationally important site for the species. Other teal winter as far south as North Africa and up the Nile Valley.

Watch a flock of feeding teal and it soon becomes apparent that they favour shallow water, dabbling to feed on the seeds of aquatic plants (these make up some 75% of the winter diet) and small invertebrates. In some areas, though, they have taken to using winter stubbles. This reliance upon shallow water makes them vulnerable to severe winter weather. Low temperatures and the freezing over of the shallows drives the birds to undertake cold weather movements, taking them further south and west in search of open water. Such movements usually drive our birds down into western france and Spain, where they occupy sites that are only important when the weather is particularly bad further north. Although a quarry species and popular with waterfowlers, temporary bans on shooting during severe weather help teal to feed on unfrozen waterbodies in relative peace. This can make an important difference to birds that are energetically stressed and needing to maximise food intake.

Assuming that we do not get a hard winter, then many of the teal presently in Norfolk will remain here until at least the end of February, when the spring departures begin. Since the spring migration is something of a protracted affair, many of the birds will still be here in late March or even early April. Arrivals back on the breeding grounds, and indeed the breeding grounds chosen, will depend on local weather conditions, again highlighting the fluidity of movements shown by this delightful species.

Wednesday, 12 December 2007

A late butterfly

The other afternoon, whilst walking home for lunch, I came across a red admiral butterfly, flying strongly above a high stone wall. This is my latest record for an active red admiral but perhaps it should not be that unexpected. The red admiral seems to be responding to global climate change, with very many more individuals seen on the wing in Britain now than was the case back in the 1970s. Some of these individuals are overwintering successfully as adults, with reports of territorial males and egg-laying taking place in the first three months of the year. This is particularly interesting because the red admiral is really a migrant visitor, breeding here in summer but thought unable to survive our winters. The first of the summer migrants reach us from the end of March, arriving from North Africa and the warmer Mediterranean islands. This means that those seen in January and February are likely to have overwintered here. Larger numbers of migrants arrive in late May or June, with these individuals originating from Spain and Portugal. The summer arrivals lay their eggs on nettles; the larvae that emerge making a simple tent by folding over the leaf and then holding it in place with silk. It is these youngsters that, having undergone the amazing transformation of metamorphosis, are seen on the wing as adults from August to October, when peak numbers occur.

From mid-August, perhaps triggered by shortening day-length, the strong-flying adults begin to move south. Large numbers often congregate in the extreme southern parts of England before crossing the English Channel. Yet, over recent years, increasing numbers have been seen on the wing later into the year to the extent that November records have become commonplace in some parts. Unlike certain other species, which as residents do overwinter here as adults, the red admirals on the wing so late into the winter usually perish. While peacocks, brimstones and small tortoiseshells choose sheltered sites for hibernation, the red admirals seem to settle on tree trunks (a site used for roosting at other times of the year). This would seem to make them more vulnerable to predators, parasites and the worst of the winter weather. Red admirals have also been reported overwintering as eggs, larvae and pupae and, in all cases, the development time of each particular stage is slowed. Once again, this may leave them open to predators and disease, leading to high losses and reducing the chances of successful overwintering.

No doubt things are changing, with more red admirals overwintering. However, since spring abundance is not correlated with the number seen late in the autumn, it seems that our increasing summer numbers result from migrants rather than those that try to overwinter.

Tuesday, 11 December 2007

Creating a living landscape

Norfolk boasts an impressive array of nature reserves, from the well known coastal marshes frequented by birdwatchers through to small blocks of woodland tucked away in the centre of the county. Each reserve tends to be managed in a particular way and benefits a particular suite of species, with some reserves managed for just one or two high profile species. Although there is no questioning the role and value of such reserves, I have sometimes felt a little uneasy about the way in which we seem to partition nature off from the wider countryside. Sure, we can defend our efforts by saying that we are seeking to protect wildlife in these few remain patches of habitat but is this enough? By accepting these small and often isolated patches as being for nature, are we not just allowing the desecration of the remaining countryside? There is a danger that nature reserves simply reinforce the perception that nature can only occur where we allow it and, ultimately, this divorces us from the world around us.

It is welcome news, then, that the Wildlife Trusts have just announced a new approach to conserving and protecting our wildlife. Accepting that many nature reserves will not be sustainable in the longer term, not least because of the effects of global climate change, the Wildlife Trusts have launched a series of landscape scale projects under the banner of ‘A Living Landscape’. This approach adopts a different philosophy to that employed for most current nature reserves by seeking to protect landscape-scale features. By definition this approach requires a thorough understanding of what constitutes a particular landscape in terms of its wildlife, habitats, geology and geography. With this knowledge it should be possible to determine how the various habitats associated with the landscape can be enhanced or restored to create a landscape that is sustainable over the longer term. It is, very much, a holistic approach. In the formerly well-wooded low Weald of Sussex, the local wildlife trust is working to enhance the fragments of remaining ancient woodland, by re-establishing lost woodland and connecting the isolated blocks together. A similar approach is being adopted by the wildlife trust in Cambridgeshire, where the Great Fen project aims to restore some 3,700 hectares of lost fenland. With time, such projects should benefit a great number  of species and, importantly, allow them to exist within a landscape that is viable over the longer term.

Of course, a landscape level approach has one other clear benefit; it reinforces the view that we need to live sustainably within a landscape. This means that such projects need to involve landowners, integrate with wider government policy and involve local communities. Only then will we have a living landscape.

Monday, 10 December 2007

A red-letter day

It has been something of a red-letter day, thanks to a pair of long overdue encounters on my local patch. As normal, I left home in darkness, heading out to the forest where I exercise the dogs with an early morning run. Passing through the wedge of arable land that sits between town and forest I stumbled across a barn owl. Its pale form stood out from the disappearing darkness like some wondrous spirit, as if absorbing the slowly-brightening half-light of early morning. This bird was so pale that it had to be a male and I had inadvertently flushed it from the rather battered hedgerow that bordered the road. On the wing the bird became more ethereal, seemingly all wing and very little body. The broad, rounded wings enable the owl to move through the air with an almost silent and effortless ease; many a time when botanising I have been surprised by a barn owl passing silently over my head, quartering the ground for small mammal prey. To see such a bird at close quarters, especially in the soft, understated light of daybreak, always sends a shiver through my body. It is a shiver of delight and not one of fear, even though owls have always been associated with the supernatural and sometimes feared as harbingers of ill-fortune. However, as this owl slipped away across the field and out of view it brought me not ill-luck but good fortune.

Less than an hour later, as I was rounding a bend in the forest ride, the dogs stiffened and stood erect, their eyes fixed ahead. Catching up with them, my gaze fell upon a group of four fallow deer, the first I had seen in this patch of forest for many years and the first live ones I had encountered for some months (there is a stretch of road to the south of Thetford where I often see the sad remains of fallow hit by motor vehicles). These four were all does, three of the dark form and one of the white form more often seen in deer parks. The dogs know well enough not to chase but were clearly unsettled by the deer. The fallow were equally unsure, standing quite still and watching us intently; the first movement from me or the dogs and they would be off. We could only have remained motionless for a dozen or so seconds but the encounter seemed timeless and I was able to take in the delicate beauty of their form and the deep intensity of their stares. Then they were gone, off the track and into the undergrowth, and the moment had passed. To have two such encounters made it a very special day.