Saturday, 13 December 2008

Return of the native

Of all our common birds, it is the native Sparrowhawk that seems to stimulate the most debate. Vilified by many because it is a predator of other birds, the Sparrowhawk has been the target of those who believe that the declines of many smaller birds can be laid at the door of a recovering raptor population. In some ways it is easy to understand why fingers of blame should be directed at the Sparrowhawk. Its population is recovering from decades of persecution and the creeping effects of now-banned pesticides. With this recovery has come an increasing use of gardens, where the Sparrowhawks may take birds that have gathered to feed. For many garden birdwatchers, the sight of nature ‘red in tooth and claw’ is distressing and they feel a certain amount of guilt that such a predator should treat their garden as an avian diner.

Sparrowhawks are dependent upon smaller birds and in years when the abundance of such birds falls so does Sparrowhawk breeding success. This link between predator and prey populations is one that has been well studied and, as ecological theory would predict, there is no evidence to suggest that Sparrowhawks have, in any way, brought about the widespread declines seen in species like Tree Sparrow, Song Thrush or House Sparrow. All of the available evidence points instead to changes in the nature of our countryside and the ways in which we exploit the land; highlighting, for example, how agricultural intensification has driven many of the observed declines.

To my mind, many of our reactions to the Sparrowhawk as a predator come from our own cultural values. We seem to value some creatures above others. Birds and mammals come at the top of the list and reptiles, amphibians and various invertebrates come much lower down. Even within groups there is a clear hierarchy – we like hamsters but don’t like rats. So, while we might welcome the Kestrel (which feeds mainly on small mammals), we don’t tolerate the Sparrowhawk because it feeds on the very birds (like Robins and Blackbirds) that come near the top of our list of cultural value. Think of your own garden; is there any indignation when a Blackbird pulls a worm from your lawn or when a Song Thrush smashes open the shell of a snail? No? Then, why should there be an outcry when a Sparrowhawk kills a Starling? All these different acts of predation are part of the natural system; all involve native species; so is it right that we should pass judgement on what is and what is not acceptable? The return of our native Sparrowhawk should be celebrated as a conservation success story and not used as a scapegoat for our own failings.

Friday, 12 December 2008

What to do about non-natives

The other week I attended a conference in Peterborough on non-native birds; species that had become established within Britain, not through natural colonisation but as a direct result of our own actions. Typically, these were birds that had either escaped from captivity and established feral populations, or been deliberately released by those who thought that they would make a good addition to our native fauna. I was presenting a paper on Eagle Owls, looking at the potential impacts of this large predator on other species now that it had established a small breeding population in the north of England.

Some of the introduced species are obvious, notably many of the exotic ducks and geese that have become established over many decades. Species like Canada Goose and Egyptian Goose are now well established and, while seemingly innocuous, bring with them their own problems. Then there are other species, like Ruddy Duck and Ring-necked Parakeet, which give greater cause for concern. Introduced from North America, Ruddy Ducks now breeding in Britain turn up in Spain where they interbreed with the endangered (and native) White-headed Duck, threatening its very survival. Ring-necked Parakeets now have a population numbering many thousands of birds, centred on London and threatening native species which rely on the same types of nest site. Additionally, the parakeets damage the economically valuable horticultural industry with its heartland in Kent.

As well as such obvious and high profile additions to our fauna (and flora – think of Rhododendron, Japanese Knotweed and Buddleia) there are many hundreds of other species that have become established, many of which we think of as native simply because they were introduced such a long time ago. Included within these are creatures like Fallow Deer, Little Owl and Brown Hare, the latter seemingly an Iron Age introduction from Denmark or the Netherlands. Because we tend to think of these species as being native this clouds the issue of what to do about other introduced species. Is it right to wish to eradicate one particular introduction but tolerate another? Purists might argue that any species that has been introduced to a new area by Man should be removed, but what if the species in question has been here for many hundreds of years without any negative impact on our native wildlife? Others might argue that we should accept that such species are here, would be difficult to remove and so we should just learn to live with them.

There are clear cases, however, where an introduced species is a real threat and should be controlled. For example, the eradication of introduced cats, goats, pigs and rats from British Overseas Territories is essential if we are to prevent the extinction of several endemic bird species.

Thursday, 11 December 2008

Snow answers some questions but raises others

The brief appearance of snow at the tail end of November brought a taste of winter proper and a temporary end to the dull overcast days that had gone before. That the snow had settled provided the impetus that I needed to take a walk out along the river and down to the lakes. Even though the snow had fallen during the morning, rather than overnight, I hoped that it might reveal the presence of some of our less obvious mammals.

Many other people had also been tempted out by the weather, a brisk walk in a crisp white landscape providing tonic for the soul, and I found that the paths were already heavily marked by the passing feet of visitors and, more often than not, their four-legged companions. It was not until I reached one of the more remote sections of the river that I had virgin snow over which to cast my gaze. Here, at last, were clear prints of animals that had passed this way within the last few hours. Most of the prints were of Pheasant, but here and there other avian tracks revealed the oversized feet of Moorhen and the clumsy waddle of Canada Geese.

I skirted the lakes and headed towards the Badger sett. Although I did not expect to see any sign of the Badgers themselves, I hoped that the snow might reveal what other creatures were making use of the spread of tunnels that occupied this outcrop of sandy geology. Approaching the sett from the north, a set of tracks crossed my path. These were Fox prints, recognisable by the distinct narrow paw with its intersecting diagonals falling between the pads. I followed the trail, brushing up against gorse and ducking under low branches. Although the tracks led up towards the sett, they avoided the dark holes and crossed instead over the top before disappearing across the nearby field. Had this Fox been beating his bounds just moments or hours before my arrival? Was he watching me now, from the cover on the other side of the field? I turned my attention back to the sett but no other tracks were to be seen around the entrances; if only the snow had fallen overnight then more may have been revealed.

Skirting the edge of the wood I began to follow my route home, stopping briefly to study the prints left by a Stoat that had emerged from cover on one side of the track, paused in the middle and then bounded up the slight incline and away. There were also Rabbit and Brown Hare prints here but no sense of the sequence of events. Which of these creatures had passed by first and had they interacted?

Wednesday, 10 December 2008

Short-eared Owls sweep the marshes

The Short-eared Owl is one of our most enigmatic birds; a scarce breeding species that favours some of our more remote and wild places. It is one of those birds that you cannot really expect to see every year without a degree of luck or a certain amount of effort. The Short-eared Owl can justifiably be described as a nomad, its breeding range extending across much of the Northern Hemisphere, from North America and Iceland, across Europe and Asia to the Pacific. There are even isolated populations in South America, on the Falkland Islands and, incredibly, the Galapagos. Young birds from the British breeding population have been found in Ireland, Spain, Malta and even Russia, further emphasising their nomadic nature.

It is fluctuations in the populations of their favoured small mammal prey, predominantly voles, that can drive these nomadic movements. In years when voles are plentiful, the owls have a good breeding season and produce lots of young. If the abundance of voles then declines so the owls are forced to wander more widely in search of prey. Some idea of the influence of small mammals in driving the numbers of owls recorded within Norfolk can be seen from a count of 116 roosting together along the Fleet wall at Halvergate in December 1972; the following winter saw just three birds in the same area.

One of my most enduring memories as a birdwatcher is seeing Short-eared Owls arrive in off the sea during autumn. These were likely to have been Scandinavian birds, given the location, but many of those wintering within the county will have come from breeding populations located in the uplands of northern Britain (from the Peak District north into Scotland). Newly arrived birds may remain on the coast, hunting over salt- and grazing-marshes, but they may also range widely, visiting farmland and inland heaths. As well as taking small mammals, the owls will also turn their attentions to small birds, particularly those species that roost or feed communally. Studies of Short-eared Owl diet have highlighted the importance of Dunlin, Skylark, Starling and Ringed Plover. Many individuals seem to take what is available but some individuals show a degree of specialisation, targeting one particular species, such as Brown Rat.

Hunting Short-eared Owls work an area in a similar manner to a hunting Barn Owl, quartering the ground for prey. Unlike the Barn Owl, however, the Short-eared will readily roost on the ground or in low scrub. Over the last few weeks at least two Short-eared Owls have been hunting over the grazing marshes just east of Lady Ann’s Drive at Holkham. Others have been reported from the Broads and the Fens.

Tuesday, 9 December 2008

Bramblings out in an appearance

Small numbers of Bramblings have been appearing in local gardens over recent days. This striking finch, a close relative of the Chaffinch, is a winter visitor, arriving in varying numbers from breeding grounds that extend across the northern forests of Scandinavia, Finland and Russia. Substantial breeding populations occur in these northern forests and, from September, they begin to move south in search of Beech mast ­– a favoured food. Huge flocks will form in areas where there is a substantial supply of this tree seed and roosts in excess of 200,000 birds are not unusual. As with many other trees, the quantity of seed produced can vary dramatically between years and it is this variability that determines the numbers reaching our shores. In years when the mast crop is poor elsewhere then good numbers arrive here; when the crop is good elsewhere then the birds remain on the Continent.

If you look in your bird book you will almost certainly be presented with a striking picture of a male Brambling in his breeding finery; the peachy pink to orange breast and shoulders and the glossy back head. However, the winter plumage is less showy, with the black hidden by paler feather tips that gradually wear off as winter passes. These winter males, however, do remain sufficiently different for you to notice them among the visiting Chaffinches alongside which they feed. As with most birds, the females have a more subdued appearance and can easily be overlooked if you simply scan across a group of feeding Chaffinches. In flight, their white rump stands out, unlike the green rump seen in Chaffinch.

Although Bramblings will visit hanging feeders for sunflower hearts and mixed seed, they seem to prefer to feed on the ground. As such, you can attract them in by feeding a mix of peanut granules and premium bird seed on a suitable piece of ground within your garden. You might also find them feeding on the ground beneath Beech trees, particularly where such trees are planted next to a road. Passing vehicles crush the Beech mast, helping the birds to get at the contents. Sadly, this habit of exploiting an easy meal sometimes lands the birds in trouble, by exposing them to the risks of collision with motor vehicles. One large roost in Merseyside was devastated by traffic, the birds having become incapacitated by salt that had been applied to the icy road surface from which they were taking Beech mast.

Results from the BTO’s weekly Garden BirdWatch survey show that the numbers of Bramblings visiting gardens do not peak until March, so having them visit now suggests that you will continue to see them for a good few weeks yet.

Monday, 8 December 2008

The familiar becomes unfamiliar

As the fog concertinas the landscape, so trusted horizons are lost and the countryside takes on a very different feel. With no sense of any real distance it is the closest hedgerows and trees that draw the eye, their bare limbs and branches stark against the flat sky becoming two-dimensional in appearance. The ragged-winged forms of Rooks materialise from the gloom and pass overhead like fragments of black cloth on an unfelt breeze. Sounds, too, are diminished, muffled by the fog, and I feel I am submerged within an unfamiliar landscape. For some reason such days suggest a more ancient countryside, a land of wet fens and wild woods, and I half expect to see the dark shapes of lost tribes emerge from the fog; perhaps a shadowy band of Vikings, fresh from their victory over Edmund. It is a strange feeling to experience but in some way it is also reassuring to feel some connection back through time with those who must also have passed over this land many centuries ago.

These damp days of early winter often bring with them a sense of melancholy that I find hard to shake. Perhaps it is the damp itself and the way in which its chill penetrates through layers of clothing to reach the bone within. More likely, it is the lack of the sun and its warming rays, rays that on a brighter winter’s day would lift my mood. While I feel hemmed in by the shortened horizons and deafened by the silence, my sense of smell is alive to the odours that are magnified by the damp and decay around me. I can smell the scent of leaf-mould as well as the more earthy odours of fungi, and a Fox that must have cut across the track some hours before.

In many ways I feel that I am experiencing my local patch anew; the familiar views have changed so much because of the fog that I almost lose my bearings. Certain trees gain in importance, appearing larger and more imposing now that they have been separated from their background. The fog also serves to shorten the day and it feels like late afternoon, even though it is not yet time for lunch. Elsewhere, the blocks of plantation forest seem more threatening, their dark depths more foreboding and devoid of life. Even so, it is good to view this familiar part of my landscape in a way that is new, to feel uncertain about an area that I so often take for granted. While the presence of the fog has unsettled me, it has also forced me to look at things in a different way and sometimes this is a good thing.

Saturday, 15 November 2008

A blustery day

I appreciate days like this; a bright clear blue sky which brings out the best of autumn’s tonal palette, coupled with a fresh wind that carries a hint of winter chill. It is the kind of weather that makes you feel alive, as each of your senses is stimulated in turn. Other creatures also seem to respond to the conditions. The local Jackdaws, for instance, have adopted an almost playful attitude. They rise up from the chimney pots on arched wings, allowing the breeze to pick them up and then fling them across the sky in a controlled glide; an arc of ragged black and sooty grey accompanied by soft cackling calls. This game continues for some time, pairs of birds seemingly enjoying themselves and immersing in an activity that appears to serve no other direct purpose. For an instant the game is interrupted, as the Jackdaws spot a Carrion Crow which has strayed too close to the patch of sky that the Jackdaws regard as their own. Working in unison they harass the crow, lunging at the bigger bird  from above and forcing it to twist and swerve in order to avoid being hit by outstretched claws or a stabbing beak. The crow responds by calling but the Jackdaws are soon successful in driving it away.

While some of the local trees have shed their leaves, others are retained and with the wind compose an overture of noise, like a succession of waves pulling back across the small pebbles of a beach. Many of the leaves retain some green, the process of drawing back nutrients not yet complete. It won’t be long until these leaves fall, perhaps prompted by another night time frost. There does not seem to be much fruit on many of the hedgerows, a few haws and hips but little in the way of tree seed. This suggests that it might be a difficult winter for some birds and I would expect to see greater use of garden feeding stations by species like Coal Tit, Chaffinch, Nuthatch and Woodpigeon.

Over recent weeks both squirrels and Jays have been working hard to store seed for the months ahead and, no doubt, some overlooked seeds will germinate in our flowerbeds come spring. Some may be unearthed earlier as bits of garden are reworked during this season when so much of the groundwork is done. This is another reason to relish the outdoors on such a day. Stand still too long and you will feel the cold but get stuck into some outdoor chores and you’ll keep yourself warm, ending the day with a healthy flush across your cheeks and deserving of a warm bath and a comfortable spot inside as darkness falls.

Friday, 14 November 2008

In praise of the pond hen

There are five Moorhens on the old pond at the moment, their stuttering swimming strokes tracing lines through the waterweed as they move in and out of shadow. It seems that just about any piece of water will suit them, from the extensive reedbeds of coastal marshes through to the sunken hollows of the larger grassy fields.

The Moorhen has long fascinated me, seemingly innocuous and predominantly sedentary, you might think that it has little of interest to offer the observer. Yet, nothing could be further from the truth. This is a bird of contrasts; a cooperative breeder (whose early brood young may stay on to help rear later broods) but which is not averse to dumping eggs in the nests of neighbouring pairs. While our populations are largely sedentary, those from further north are migratory in habits. Other aspects of the annual cycle are equally interesting.

The long breeding season begins early in the year, with the first eggs laid from the middle of March, and the season itself continues through into August. The first nests are often predated, perhaps because of the lack of nesting cover so early in the year. Undeterred, pairs will lay repeat clutches and many may rear two broods over the summer, with some managing to raise three. Then there are the nests themselves. Moorhens make three different types of nest. The first to be built are the display nests; these consist of sedges, reeds and dead twigs and are used for sexual display and, ultimately, coition. The first of these may be constructed from late February onwards, with some territories sporting up to five such platforms. Then there is the egg nest, built from fresh or dead water plants, usually on the ground within shallow water. The size of the nest may be enhanced if water levels rise. Very occasionally the nest may be built in a bush, possibly several metres above the ground and on top of the old nest of another species. Finally, there are the brood nests; constructed soon after the eggs hatch, these provide a refuge for the young chicks.

At this time of the year, however, the Moorhens are more concerned with finding sufficient food to get them through the winter. Many pairs will remain on their territories as long as they have access to open water. Should these ice over then the birds will be forced to move elsewhere, possibly onto neutral areas where they will feed alongside other birds. Even here, they are fun to watch and we are fortunate that our Moorhens are so trusting of Man. In other parts of their range, where they are a table bird, they tend to be shy and retiring.

Thursday, 13 November 2008

Red-flanked Bluetail draws a crowd

The North Norfolk coast remains a real draw for birdwatchers and tends to be busy most weekends throughout the year, something which can prove a frustration to the locals upon occasion. The residents of Weynor Gardens, for example, could be forgiven for subscribing to such a view the other weekend, when large numbers of birdwatchers arrived to see the Red-flanked Bluetail that spent several days at Muckleburgh Hill. This particular site has a good track record for hosting wayward migrants in autumn and is always worth a visit if the weather conditions look favourable during late September and October. Unfortunately, parking is an issue if something rare turns up and this particular weekend was no exception. I have never enjoyed the crowds that can gather at ‘twitches’ and would have avoided making a visit to Muckleburgh Hill were it not for having a kind and understanding friend who owns one of the houses that border Kelling Heath.

Although the road was lined by cars, the crowd watching the bird was surprisingly small, in part because the bird was mobile and folk were spread over a fair area. The bird itself, a very rare but increasing vagrant from the Russian Taiga, was working the available cover, dropping down periodically from the compact trees to feed on the ground or from low exposed branches. Slightly larger than a Robin, the bluetail was a very smart little bird. Similar in general structure to a Redstart, it showed the blue tail and orange flanks which give the bird its name. This was either a female or a first winter male and so had grey-brown upperparts and lacked the dirty blue plumage of an adult male. Even so, it oozed personality as it flitted down to feed before flying back into cover. As it moved between little patches of cover, so the back of the watching crowd suddenly had front row seats and, with a well-behaved crowd, the audience were treated to a delightful performance.

Curiously though, the bluetail was almost upstaged by the presence of a Spotted Flycatcher – an exceptionally late record and presumably a migrant from further east that had also been blown across the North Sea. The 2006 Bird & Mammal report gives a record late date of 26th September, so this bird was many weeks later than would normally be expected. The quality of Muckleburgh Hill was further emphasised by the presence of a Firecrest and at least one Chiffchaff. All of these birds were duly noted in my field notebook and, once home, were entered onto the BirdTrack system ( developed by the British Trust for Ornithology. This means that they will feed through into the Bird Atlas 2007-11 and reach the County Bird Recorder.

Wednesday, 12 November 2008

Adversity can promote a long life

I was raised within the sylvan embrace of the Low Weald; a well-wooded strip of country that rests on an ancient geology, now exposed with the eroding away of its covering chalk dome. To grow up among trees has left its mark on me and I always feel more comfortable in their presence. Yet, as I have mentioned before, trees have become an almost unseen backdrop to our lives. Their size and longevity, coupled with the fact that they remain rooted to one spot, seemingly makes them inconspicuous to casual observers. This also means that we tend to treat them badly, using them as architectural features – hemmed in by roads and pavements, or cutting them back indiscriminately because they block our view or shed leaves where we do not want them.

It is also fair to say that we do not, by and large, understand trees or fully comprehend our impact upon their lives. We have this conception that trees mature, become full of decay and, by doing so, reach the end of their lives. However, decay is part of the normal development of a tree and many trees will undergo retrenchment, reducing the area over which new wood has to be laid down by shedding branches and twigs, before going on for many more decades. While trees lack both an immune system and a wound repair system, they can wall off and bypass damaged tissue, effectively allowing them to redirect growth in a new direction and to balance this against incoming resources.  This whole idea that trees have a defined lifespan and die of old age is something of a myth, for most trees are felled before they even reach middle age.

How long a particular tree has left to live, our intervention excluded, has little to do with how old it is but far more to do with its size and rate of growth. The truly veteran trees of Europe are not the oaks of landscaped parkland with their spread of great branches; instead they are the small twisted forms of cypresses, growing slowly on the high slopes of Cretan mountains. For those trees that have in some way been managed by Man, it is those that have been pollarded which tend towards longer life. In both cases, it is adversity which has prolonged life, by slowing the rate of growth. Since so much of a tree’s fortune will depend upon our influence, it is we who determine how they live and when they will die. Oliver Rackham, the great woodland ecologist, summed this up just perfectly when he said that when it comes to life expectancy in trees the ‘battlefield’ is a better analogy than the ‘almshouse’.

Tuesday, 11 November 2008

Some chirpy birds

At least one small group of Crossbills has been active around Croxton Heath over recent days, their chirpy calls expressed like a group of overexcited children on their first independent outing. I seem to catch up with them most mornings and they provide a new backdrop to my early morning walks. Their loud, metallic-sounding calls are a welcome addition to a soundscape that is much diminished with the approach of winter (the wistful Robin and ever present Wren my usual companions).

The presence of these robust little birds owes everything to the dark plantations of pine and, in particular, spruce, upon whose seeds the birds depend. The changing fortunes of the Crossbill within Norfolk owe much to the establishment and subsequent maturing of these conifers, an increase in feeding opportunities and nesting habitat. The primary source of these birds, however, is the great tract of boreal forest that stretches across Scandinavia and east towards the Pacific. This great forest supports the Crossbill populations from which our far smaller population is derived and, in many years, supplemented.

Crossbill populations are so dependent upon the conifer seeds that they will quickly vacate large areas within which seed supplies have been exhausted. This results in large-scale irruptive movements, the birds tending to move in early summer once they have finished breeding. Breeding itself normally takes place incredibly early in the year, during late winter to be precise, and there are even old Norfolk records of incubating females seen with fresh snowfall around them. Such early breeding means that some pairs will be egg-laying in the latter half of December. The irruptive nature of Scandinavia populations brings new arrivals into Norfolk in numbers that can vary dramatically from one year to the next. These birds can turn up in unusual situations – we once caught one in a reedbed – but ultimately they supplement our key breeding populations in Thetford Forest, in the woods around Sandringham and along the Holt to Cromer ridge. Breeding was first documented within Breckland in 1815, when a nest was taken at Livermere, and is certainly considered an annual occurrence now.  As well as winter breeding records, there are occasional records of birds breeding in late summer, some of which may include youngsters breeding in the same year in which they were born.

The future of our breeding Crossbills is dependent upon a number of different factors, including the form and age of our conifer plantations. Many of those within Breckland are currently at an ideal age  but these will soon be felled and this will diminish the resources available to these delightful little birds. If we want to keep them then we need a good mix of trees of differing age.

Monday, 10 November 2008

A touch of gold

Norfolk is well known for its great expanse of farmland; the huge fields are dominated by arable monocultures and there are few hedgerows or woodlots to halt the eye as you across the horizon. On dull winter days such fields can seem rather bleak; the dull shades of landscape merging into those of overcast skies, but with a frosty morning the earthen colours are warmed and lifted by the brightness of a clear blue sky. It is on such days that I like to search the fields for wintering waders and wildfowl. Towards the coast, fields may be crowded with feeding geese, pink-feet and brents, while inland they are dominated by waders like Lapwing and Golden Plover.

The Golden Plovers are a winter treat; birds from the upland breeding populations of northern England and Scotland are joined by those from Norway, Iceland, the Faeroes and even the westernmost parts of Siberia. Invariably, they can be found feeding alongside the noticeably larger Lapwings. It has been shown that the Golden Plovers actually use the presence of their larger cousins to indicate rich feeding opportunities. An arriving flock of ‘goldies’ (as us birdwatchers often call them) will drop down and land amongst the Lapwing, individual birds then adjusting their position within the flock on the basis of how well other birds seem to be feeding.

Nationally, our wintering Golden Plovers prefer to feed on earthworm-rich pastures but in Norfolk such pastures are uncommon and the birds associate with sugar beet, winter cereal and newly-planted oil seed rape. Flocks will use different areas for roosting and feeding but many seem to return to traditional sites from one winter to the next, making it relatively easy to track them down. However, birds will move in response to hard weather. If it is cold on the Continent then more arrive here; if it is cold here then the birds move off elsewhere. Much of the activity actually takes place at night. Simon Gillings, one of my colleagues at the British Trust for Ornithology, has spent a number of years studying the birds and their nocturnal feeding habits. He found that up to 80% of birds feed at night, often on fields some distance from where they had spent the day.

The flocks are worth scanning for other reasons, not least because the ‘goldies’ and Lapwings are sometimes joined by other birds. Just recently, near East Harling, one particular flock of plovers also held an American Golden Plover and a Dotterel ­– two really good birds for this part of the country. Black-headed Gulls are quite often found with the flocks, attracted by the easy pickings they can obtain by robbing the plovers of newly extracted earthworms.

Saturday, 18 October 2008

Watch out there's a stoat about

The Stoat is one of those animals that I only see occasionally, perhaps running across a track or working the base of a hedgerow in search of small mammals or other prey. As such, I tend to take notice of where and when I see Stoats, noting them in my field book to report at the end of the year. It seems that I am not alone in this; look at the Norfolk Mammal Report (available from the Norfolk & Norwich Naturalists’ Society) and you will see the species features more often than others that you would consider to be more common across the county. Does familiarity breed contempt and are we ignoring the commonplace?

There is something mesmerising about a Stoat that is working an area in search of prey. Ever alert, it searches opportunistically, pausing every now and then to scan for other predators and would-be prey. I have only seen a Stoat tackle prey on a handful of occasions, usually a vole or mouse, but on once a Rabbit considerably larger than the Stoat in size. Stoats are reputed to mesmerise their prey by dancing but this is unlikely to be the case. The few incidents where observers have reported such behaviour may, in fact, be observations of a Stoat suffering from an infestation of a parasitic nematode, which causes skull deformity and spasms.

Although the Stoat is one of the smaller European carnivores, it is not the smallest and shares the British part of its wide range with the even smaller Weasel. The two species can be told apart fairly readily; the Stoat larger, with a long black-tipped tail; the smaller Weasel with a shorter tail and no black tip. Additionally, in Stoat, the chestnut back and flanks meet the cream belly in a straight line, whereas in Weasel this line is irregular and sometimes spotted.

There is one other aspect of Stoat ecology that fascinates me and that is its breeding system. Both male and female Stoats are territorial, with each male holding a territory within which there may be one or more smaller female territories. During the breeding season each male will adopt one of three strategies, the choice dependent upon his age and social status. Older dominant males adopt a roaming strategy, expanding the size of their territory massively. They then roam around the territory in search of females, spending a few days with each before moving on. Younger males stay within their smaller territories and the youngest males remain fully transient, unable to hold a territory of their own. Although mating occurs from April to June, the females delay implantation, so the resulting young are not born until the following spring.

Friday, 17 October 2008

Bush crickets make the most of autumn sun

I try to make the most of any late-autumn warmth by getting out into the field, treating each warm and sunny day as if it might be the last one before the onset of winter. While a bright morning might start with a nip in the air, it often warms as the sun rises and the small numbers of summer insects that remain can be seen on the wing or crawling across the surface of some fading leaf. The warmth of last weekend drew me to the coast and to some of the small lanes that drop down towards the beach at places like Kelling and Weybourne.

One particular stretch of low hedgerow, dense with bramble and in full sun, was alive with the sounds of calling bush-crickets. It is late in the season for these insects and many of the Breckland populations have fallen silent over recent weeks, possibly due to the handful of night frosts that we have already experienced. Here on the coast, however, there were good numbers of Dark Bush-crickets repeating their short chirping song at irregular intervals. The song is high-pitched and while I can still hear it, my birdwatching companion no longer can. With patience I was able to locate a couple of the calling individuals and point them out. Each robust and dark individual, about two centimetres in length, was calling from just within the bramble cover, producing its call by rubbing its modified wings together.

Typically, in male bush-crickets, the base of each wing is modified, with a tooth-bearing rib present on the underside of the left forewing. This is rubbed against the edge of the right forewing, next to which is a modified area, known as the ‘mirror’, which amplifies the sound that is produced. Only the Oak Bush-cricket lacks this adaptation; the male instead tapping out his drumming call with a hindleg onto whatever he happens to be standing on.

Dark-bush Crickets are robust creatures and have a long season, lasting through until the first frosts of late October or November. However, other bush-crickets are more strongly influenced by temperature and so I was a little surprised to see and hear two calling Roesel’s Bush-crickets in the same stretch of hedgerow. Roesel’s Bush-cricket is a species that has expanded its range northwards over recent years, a result of global climate change. First recorded in Norfolk in 1997, its colonisation of the county has been extremely rapid. Hot summers can boost numbers and while the 2008 summer may not have been the best, the species has clearly been fairly successful. Let’s hope they continue to call for a few more warm and sunny mornings.

Thursday, 16 October 2008

The first geese

The first of the winter’s geese are here and the morning sky echoes with their calls, as long skeins move between overnight roosts and daytime feeding grounds. These are Pink-footed Geese, newly arrived from breeding areas in Iceland and eastern Greenland, and their numbers will continue to grow over the coming weeks. Virtually the whole of the Icelandic and Greenland breeding populations winter in the UK, some 250,000 or so birds and representing at least 85% of the World population. The only other breeding population can be found on Svalbard and individuals from there winter in The Netherlands and, increasingly, Belgium.

These Pink-footed Geese will have arrived in Scotland several weeks ago, the arrival there continuing through into the middle of October, before most filter south through staging areas to favoured wintering grounds. The bulk of the population winters either in Lancashire or East Anglia, and Norfolk itself is a very important county for this winter migrant. The latest WeBS report, published by the British Trust for Ornithology, shows that the Wash and the North Norfolk coast currently supports some 59% of the UK wintering population.

The geese are attracted by the combination of undisturbed roosting sites and daytime feeding areas. Initially, the geese wintered and fed on saltmarsh, feeding on grasses and herbs on the short saltmarsh sward. More recently the birds have taken advantage of the food available on areas of arable land and pasture, with sugar beet tops and waste potatoes a favoured food. Such choice does bring a small amount of conflict with landowners if the geese move from the harvested beet fields to feed on growing crops elsewhere. This can happen if the geese suffer high levels of disturbance when feeding on the beet, so landowners often grow the sugar beet away from footpaths and busy roads; this benefits both the landowner and the geese, which may go some way to explaining why the population has increased over recent years.

To me, it is the movement of pink-feet between roosting and feeding sites that is the most evocative part of the Norfolk winter. To hear an approaching flight of geese, which first appear as a distant smudge on the skyline but which turns into distinct skeins as they approach, is truly magical. Equally magical is the sight of a huge flock, many hundreds strong, feeding across one of the larger coastal fields. To scan across these with a pair of binoculars reveals an army of individuals all feeding on the waste tops of beet. In some ways it is a shame that they are only here for part of the year but I suppose that if they were here all year round then their magical charm would become commonplace.

Wednesday, 15 October 2008

On the move

When you think of bird migration you tend to think of summer or winter visitors, such as Swallow, House Martin or Redwing; birds that are only with us for a small part of the year. This means that many of the birds that are on the move during autumn or spring go unnoticed, simply because they happen to belong to species that you would normally see throughout the year. For instance, birds as familiar to us as Song Thrush, Chaffinch and Goldfinch all either have a migratory component to their British breeding population or to a population elsewhere within wider European range.

While most of our breeding Song Thrushes and Chaffinches are rather sedentary in their habits, some winter abroad in France, Spain, Ireland or Portugal. At the same time, Britain also receives Song Thrushes and Chaffinches arriving here to overwinter, or passing through en route further south during the autumn months. A visit to the Norfolk coast soon after dawn may well reveal some of these visitors. On Sunday morning, for example, I saw and heard good numbers of Chaffinches and smaller numbers of Song Thrushes passing overhead at Kelling Quags, together with other autumn migrants – including Brambling, Siskin and Meadow Pipit.

Both Meadow Pipit and Chaffinch are diurnal migrants (migrating during the day), and the birds I saw may well have been continuing journeys initiated in Scandinavia over recent days. Some of these birds, notably the Brambling, will have made a direct crossing of the North Sea but others, like the Chaffinch, will have avoided the crossing altogether by taking a longer route around the North Sea coast, through the Low Countries and then making a short hop across the English Channel. Such a convoluted journey will have required some nifty navigational skills along the way, given the change in compass direction needed at different stages of the journey.

Another interesting aspect of Chaffinch migration (at least for the birds leaving the northernmost part of the breeding range) is the difference in timing between males and females, and adults and young. Females Chaffinches tend to move before males (and migrate further) and the same is true of young birds, when compared with adults. In the case of the Song Thrush, individuals from different parts of the breeding range show variation in their movements; those from the northernmost populations tend to move the furthest south, with some birds even reaching North Africa. What amazes me about all these movements is not simply that such small birds can undertake such large movements but how individuals of the same species can behave so differently depending upon where they were born, what sex they are or whether they are a young bird or not.

Tuesday, 14 October 2008

An exceptional occurrence

By all accounts it has been something of a poor year for butterflies, with many species present in lower numbers than those usually seen. The poor weather over much of the summer contributed to difficult times for butterflies and there were several species that I either failed to catch up with entirely or of which I saw very few individuals. As such, a recent trip to Holkham proved to be a rather exceptional event thanks to the presence of a single White Admiral butterfly. I had gone to Holkham to look for a Radde’s Warbler that had been seen there earlier in the day. While I failed to catch up with the Radde’s Warbler, the presence of a fresh-looking White Admiral, close to where the warbler had previously been seen, more than made up for my disappointment.

This is a species of butterfly that I normally see much earlier in the year, with Knettishall Heath a favoured local site providing sightings of newly emerged individuals throughout June and July. The White Admiral is univoltine, which means that it has just a single generation each year. The graceful adults are on the wing from June to August, depositing eggs on the leaves of honeysuckle from which emerge the caterpillars. Each caterpillar begins its journey towards adulthood in late summer but then hibernates through the winter to resume its growth the following year. Given that the single generation of adult White Admirals is over by the end of August, my sighting of a newly emerged adult at Holkham posed an interesting question – what was it doing on the wing so late in the year? Was this an adult that had simply emerged spectacularly late or had a caterpillar completed its growth and transformation within a single season.

Searching through my numerous books on butterflies finally revealed the answer; I discovered that a small second generation of adults might very occasionally occur in those years when the first generation is on the wing exceptionally early in the season. It seems that a handful of individuals must have been on the wing in late May or early June, with some of the resulting caterpillars completing their stage of the life cycle without the winter break. If any eggs were to be laid as a result of these very late season adults then the resulting caterpillars would presumably enter winter hibernation at a much smaller size than normal, something that might reduce their chances of surviving through to next spring. Whatever the fate of this particular late-season individual I was glad to have seen it at a time when the butterfly season is just about coming to its end.