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.