Saturday, 9 February 2008

An ideal location for a vacation

You may not realise it but your garden provides a winter retreat for a whole bunch of foreign visitors. In amongst your resident garden birds will be those that have arrived here from as far afield as Norway, Iceland or even Russia. The thing about these avian ‘tourists’ is that many of them go completely unnoticed. While visiting Bramblings, Waxwings and Fieldfares might stand out from the crowd because they don’t breed here, visiting Chaffinches, Greenfinches, Blackbirds and Robins don’t look any different from their resident counterparts. We only know that they are here because scientists across Europe regularly fit small metal rings to birds. In time, some of the birds fitted with rings are caught elsewhere by bird ringers; others fall victim to pet cats, fly into windows or collide with traffic. If somebody finds the bird, notices the ring and then contacts the address stamped into the ring, then the researchers can work out where the bird has gone and over what time period.

Thanks to the efforts of these scientists it has been possible to estimate, for example, that a minimum 12% of the Blackbirds in Britain outside of the breeding season actually come from overseas. Equally sizeable populations of various finches and other thrushes also winter here, collectively hinting at what an attractive destination a British garden makes. So why should Britain be so good in the winter? It may not seem as pleasant here as somewhere further south, for example the Mediterranean coast of Spain. However, Britain is actually surprisingly mild for its latitude during winter, warmed by the Gulf Stream and this means that birds can overwinter here in relative comfort. They are also closer to their breeding grounds than they would be if they had migrated further south. This is also advantageous because they do not have as far to go on the return leg in spring, thereby reducing the energy stores needed to get them home.

Of course, another reason why our gardens are so attractive is that they are often stocked full of food, thanks to our love of birds and willingness to feed them. Some of the visiting birds will have moved here over several months, following natural fruit and seed supplies and only reaching our shores once these stocks have run out. Not only that, but many gardens have conifers in which these birds can roost overnight, water which they can drink or in which they can bathe. So take a look out of your window and cast your eye over the Blackbirds fighting over apples on your lawn or the Starlings squabbling over your bird cake. Are these local birds or do some of them bicker with a continental accent?

Friday, 8 February 2008

Golden Gorse

Blocks of golden yellow decorate the landscape; added, like thick strokes of oil paint, to a winter canvas of more muted tones. This unexpected rush of colour is brought about by the flowering of gorse, a familiar spiny shrub of heath, common and waste ground and a great landscape plant. The common gorse flowers during late winter and early spring, bringing a welcome splash of colour and a suggestion that spring is on the way.

Gorse is a plant with a long and sustained association with Man. The name itself is said to derive from the Anglo Saxon word ‘gorst’ meaning ‘waste’, perhaps reflecting an association with the poor soils on which it grows. However, it is with another Anglo Saxon word that many know the plant today. This is ‘furze’ (‘fyrs’ in the Anglo Saxon) which highlights the use of the plant for firewood. ‘Furze’ is one of just a handful of Anglo Saxon words still in use in their original form. The use of gorse for fuel was once a widespread practice, not just domestically but also for industrial processes such as for firing West Country china clay ovens or for the baking of bread.

Gorse had a number of other uses, one of the most important of which was the provision of winter fodder for livestock. In some areas the gorse was managed like a crop specifically for this purpose, with a preference shown for the softer female form of Western Gorse (an uncommon plant in Norfolk, found only in scattered parts of the north of the county). The sharp spines, evolved to deter browsing animals, had to be crushed in a mill before being fed to livestock. Many of the mills at which the crushing took place were established specifically for this purpose. One, perhaps rather unexpected, use for gorse was in gold mining. The Romans deployed a technique called ground sluicing, in which water was used to wash gold-rich silt through a series of filter beds. The Roman engineers found that gold dust was trapped more effectively by gorse than by the other filters that they tried. Mind you, handling the filters cannot have been much fun!

There is something about gorse that makes me think that is a rather fine plant. Perhaps it is the soft vanilla smell that comes off its flowers, or that it adds a strong structural component to the open heaths and waste ground on which it grows. Whatever the reason, I am in good company in my liking of the plant. The great Swedish naturalist Linnaeus is reputed to have fallen to his knees and thanked God when he first saw gorse on an English common. A fine plant indeed!

Thursday, 7 February 2008

Swans on the up

The Fens can seem rather bleak and inhospitable at this time of the year, exposed to a wind that whips in off the North Sea and with an expanse of sky dark with threatening clouds. Yet this unique part of East Anglia attracts huge numbers of wildfowl, counted among which are sizeable numbers of our two migratory swans. Drawn to this area by the combination of secure roost sites and available winter food, whooper and bewick’s swans gather annually on the Ouse Washes, centred around the Wildfowl & Wetlands Trust reserve at Welney.

The bewick’s swans, of which 5,000 or so winter on the Ouse Washes, originate from breeding grounds in western Siberia. These birds migrate west to winter in the Netherlands, Britain and Ireland. Some 50% of those wintering in Britain gather on the Ouse Washes and, during January, the washes may be the most important site for the species anywhere in Europe. Traditionally, the swans would have grazed on aquatic and semi-aquatic plants taken from areas of marsh and flooded pasture. However, since the 1970s there has been a noticeable move onto arable land, with the birds favouring fields with sugar beet, potatoes or autumn sown cereals. The cereals become more important towards the tail end of winter. Each morning the swans leave the safety of open water on which they roosted over night to gather on the arable fields that lie just off the washes.

The larger whooper swans are among the heaviest migratory birds, with adult males averaging around 10kg. The individuals wintering here in East Anglia will, for the most part, have come from the Icelandic breeding population. Those from breeding grounds in Finland and NW Russia winter on the continent but there is a small amount of interchange between the two populations (with an estimated 200 Finish birds wintering here and 600 Icelandic birds wintering on the continent). Like their smaller cousins, the whoopers make good use of the arable land and the area around the Ouse can easily attract 3,500 individuals during the middle of winter. Interestingly, both species of swan arrive in family parties and this has enabled researchers to gain an understanding of their annual breeding success. Young birds with their parents can be readily identified and it is possible to calculate the proportion of youngsters within the wintering herds (groups of swans are called ‘herds’ not ‘flocks’). The most recent figures demonstrate that roughly 1 in 10 swans is a youngster, a figure that has declined over recent years, suggesting a decrease in breeding success. The swans will begin to depart from the middle of the month so it is worth making a trip to Welney to see this winter spectacle.

Wednesday, 6 February 2008

Tree Sparrows a welcome sight

With a patchy distribution and an unobtrusive nature, the tree sparrow can be a difficult bird to connect with. A small colony which frequented a series of farm buildings near one of my regular haunts has been absent over recent weeks and I had been wondering if I would get to see the bird locally this year. It was a welcome sight, then, to bump into three tree sparrows near Middle Harling over the weekend. Walking off a farming estate I caught a soft disyllabic chirp that immediately made me think tree sparrow. Investigating the source of the call, I spotted the distinctive chestnut-capped form of a tree sparrow, tucked into thick cover towards the base of a tree. Two others sat on the other side of the road in the shrubby cover provided by the garden of the estate’s gatehouse. This was a quite unexpected encounter, not least because I have passed this spot many times over the past few years without hearing so much as a chirp.

The tree sparrow has probably undergone a greater decline over the last 30 years than any other British bird. Although widespread across lowland Britain at the end of the Nineteenth Century, its population has been in decline since the 1930s. A slight recovery during the 1960s was linked to an influx of immigrants from the continent but since then things have taken a turn for the worse. The arrival of immigrants late in the year no doubt contributed to the flock of some 1,500 birds which frequented the Eye field at Cley for three months during the 1957/58 winter – a record modern count for the county. Things are very different today, with just a few reliable sites scattered across the county where you can guarantee seeing the species. The areas around Ringstead/Choseley and around the Cressinghams come to mind.

As with other farmland seed-eaters, the decline of the tree sparrow has been linked to changing farming practices. The loss of over-winter stubbles may have reduced food availability and contributed to a potential fall in overwinter survival. However, the species may also be facing problems during the breeding season. Feeding its young on invertebrates, rather than seeds, may leave the species open to a decline in invertebrate numbers. Tree sparrows breed quite late in the year, with most initiating egg-laying during May. Individual pairs may breed through into August and beyond, attempting two or three broods through the season. This means that I will need to return to the gatehouse later in the year to see if these birds are here to stay or just wintering alongside the various finches and buntings that make good use of the area.

Tuesday, 5 February 2008

A winter walk

The wind has dropped but clear skies overnight mean that the air carries a sharp chill and my breath clouds as I exhale. It is a fine day for a walk; the quality of the light, filtered through a brilliant blue sky, reveals every fold in the landscape and the bare limbs and branches of trees stand strong in silhouette. Crossing fields of grazed pasture, bordered by old hedgerows and occasional twisted oaks, my passing is heralded by a pair of Egyptian geese – soon to be nesting in a suitably large cavity. A flock of fieldfares, perhaps three dozen strong, chatters quietly as it moves across the short turf in search of invertebrate prey. There has been just the merest touch of frost, so the fieldfares should still be able to probe the ground.

Leaving the farmland behind I enter an area of clear fell. Now in their second year of growth, the young conifers can be seen fighting their way up through the early successional plants quick to exploit the bare soil. As I cross diagonally through the regimented lines I disturb a roe deer – a buck in his thick winter coat. He moves away but then turns to watch me, inquisitive but alert. This seems to be a feature of the roe. This buck is in velvet, his antlers sheathed in blood-rich tissue which will remain in place through into March. In adult males this annual cycle of renewal begins late in the year (from October) but starts somewhat later in young bucks. With his curiosity satisfied the roe moves off and I am alone again, save for the solitary crow that sits calling from an isolated beech.

A little further on, and warmed by my exertions and the strengthening sun, I catch sight of a kestrel. It passes low over the trees in a neighbouring block of plantation before dipping down to work one of the snag lines of twisted root plates left in place when the last block of timber was harvested. The kestrel flushes a flock of 40 or so goldfinches but seems to take no interest in them. The goldfinches rise as one to perch in a nearby birch, their delicate calls resonant like tiny chimes. It is not that often that I see so many goldfinches together and they add a splash of colour to the brown and russet tones of the forest backdrop.

It is on mornings such as this that I really appreciate being out doors in the Norfolk landscape. It may be winter but it is a fine and bright winter, with enough of the sun’s warmth creeping through to suggest that spring is not that far away.

Monday, 4 February 2008

Take up the armchair challenge

The last weekend of January saw many thousands of people up and down the country take part in the RSPB’s Big Garden BirdWatch. This annual event provides a very brief snapshot of garden bird populations and, more importantly, engages them with the concept of citizen science. Citizen Science is all about large-scale scientific studies made possible by the contributions of volunteers. For example, most of the biological recording carried out within the United Kingdom is citizen science, the records collected by unpaid volunteers used to underpin conservation policy. These volunteers are often referred to as amateurs (as opposed to professional fieldworkers or researchers). However, this title does them great disservice because many are experts in their chosen field. A more appropriate distinction would be to call them unpaid volunteers (as opposed to paid professionals).

The tremendous importance of this army of volunteers can readily be seen once you realise just how much time they give to support nationwide surveys and national projects. One organisation that clearly benefits from volunteers is the British Trust for Ornithology (BTO), whose 30,000 or so supporters collect the information needed by Government to monitor the changing status of our breeding and wintering birds.

One particular BTO project, the BTO/CJ Garden BirdWatch, deploys some 16,000 ‘armchair’ birdwatchers, who keep simple records of the birds using their gardens each week throughout the year. These records enable the BTO to examine the way in which different birds use gardens and how this use varies with season and over the longer term. Participants in the BTO/CJ Garden BirdWatch not only give generously of their time, typically spending 1-2 hours each per week watching and noting down what they see, they also support the project financially, through an annual subscription of £12. This covers all of the running costs of the project, including time for analysts to study and report on the figures, the production of recording sheets and the quarterly colour magazine that feeds information back to participants. An impressive number of scientific papers have been published based on the records collected by the volunteers, a fitting testament to their efforts in supporting this project and providing the all-important records.

The BTO/CJ Garden BirdWatch survey builds on the enthusiasm generated by the RSPB’s high profile once-a-year event. Many of those bitten by the bug that is armchair birdwatching go on to get involved in the weekly recording offered by the BTO study. By doing so they learn more about their garden birds, discovering how the patterns that they see in their own gardens fit into the wider picture of what is happening on a seasonal basis across the country. Why not get comfortable in your armchair and get involved.