A touch of the winter blues

I always find this time of year rather difficult; the damp clinging cold and drab skies do little to lift my spirits. As a morning person I resent the way in which the dark of night intrudes into my routine and limits the time that I can spend out before work. While crisp, bright winter days invigorate me, the still, overcast, rain-sodden days of late provide little in the way of cheer as I trudge along the river on my way to work. The moorhens skulk about in search of food, hunched forward as if they too are weighed down by the cheerless weather. There is, however, a spot of colour in this flat and featureless scene – a kingfisher which frequents this stretch of the river.  A dazzling, darting streak of electric blue that whirls away from me as I near its favourite perch; this kingfisher must nest nearby, remaining on its territory throughout the winter months. I remember reading somewhere (perhaps in David Boag’s wonderful book on the species) that only the righteous may witness the kingfisher. It is certainly true that, despite its bold colours, this bird is often overlooked. One reason may be its size – the kingfisher is about the size of a greenfinch, a fact that will surprise many who would imagine, never having seen one, this to be a larger bird.

I have been fortunate enough to see kingfishers in the hand, since we sometimes catch them in our nets when out bird ringing. With their short, waxy, orange feet, orange-brown underparts and electric blue-green upperparts they are incredibly beautiful. They are also very docile when being handled and move their head very slowly (like some kind of automaton) to view the proceedings. The colourful plumage once proved popular with milliners and the feathers would appear incorporated into hats. Other birds were shot for taxidermy and many were stuffed by Victorian taxidermists.

The kingfisher population has flourished over recent decades on many stretches of river. Improving water quality is likely to have played a part but it is the run of mild winters that will have had the greatest impact on the population. Very cold winters, during which the slow-moving lowland rivers favoured by kingfishers may freeze over, can spell disaster. During the winter of 1962/63, the severe cold resulted in the complete loss of kingfishers from some areas and in many others the population fell by 85%. Fortunately, kingfishers are able to produce two or three broods of young a year and so populations can bounce back quickly. While I might favour the crisp chill of a proper winter’s day, I will tolerate the damp, gloomy weather for the sake of this wonderful bird.

The sound of the countryside

For me, being out and about in the countryside is not just about what you see. It is also about what you hear, feel, smell and taste. The churring of a nightjar in the still of the forest, the rough texture of bark or the scent of fungi on a damp autumn morning. You should be able to engage with nature and immerse yourself in the world around you through all of your senses. But what if you are unable to use one or more of your senses; does this diminish your experience of nature? For most of us the answer is unknown, although we may experience some degree of loss as we age and our eyesight and hearing begin to fail. It has been calculated that roughly one in every seven people suffers from some form of hearing loss and many older birdwatchers comment on how they can no longer hear the high pitched calls of goldcrests or the echolocation of feeding bats. As I age, I wonder if I too will reach a point where I can no longer hear (and enjoy) these subtle sounds.

In an attempt to help hearing-impaired visitors engage more fully with wildlife, Norfolk Wildlife Trust has recently added a ground breaking new hearing support system to one of the hides at its Cley Marshes reserve on the North Norfolk coast. Two microphones positioned on the reserve pick up the sounds of the waders and wildfowl that use the many pools. These sounds are then fed back to the hide, where they can either be heard on headphones or via a hearing loop. Although similar systems have been employed elsewhere, the one at Cley is unique in that it is powered entirely by a combination of solar and wind power; a suitably green solution.

The system was developed by Dennis Furnell, who was himself partially deafened as a result of a car accident. Thanks to a grant from The Heritage Lottery Fund, plus equipment donations, Dennis has been able to install the system as part of Norfolk Wildlife Trust’s “Access for All” project. This also involves the production of large print leaflets for all their major reserves and an audio trail around Cley Marshes itself. Such developments are a welcome addition to what is already one of the country’s premier places to engage with a diversity of wildlife. Wildfowl and waders can be noisy birds, particularly when present in flocks several hundred strong. More people will now be able to enjoy the sights and sounds of this part of the Norfolk coast and, hopefully, feel that they have truly engaged with the birds and other wildlife that make the countryside such a special experience. 

A Christmas tune

The dark gloom of these December mornings is softened somewhat by the wistful tunes of singing robins. While all our other songsters have fallen silent, the robin continues to sing in defence of its territory right through the winter months. Holding a territory is incredibly important for a robin and it is only during the most severe of winter weather that the pattern of territories may break down altogether. Even the females may set up their own winter territories, often close to where they will breed the following season, and proclaim ownership of these through song.  The winter song contains certain phrases that denote territory ownership and these also appear in the subtly different breeding season song. What are missing from the winter song though are the sexual phrases used in establishing a bond with a mate.

There is a strong tradition associating this confiding and popular bird with Christmas and it is always interesting to see how many Christmas cards arrive with a robin on their cover.  In fact, robins first appeared on cards soon after the custom of sending them at Christmas first took off commercially back in the 1860s. David Lack, writing in his famous book ‘The Life of the Robin’, noted that the use of the robin on Christmas cards probably stemmed from similarity of the robin’s red breast to the bright red uniform worn by Victorian postmen; many of the early card designs showed a robin with an envelope in its mouth.

Despite its confiding nature, and our enduring affection for this bird, it is worth noting that the robin can be a particularly quarrelsome species. The territorial song and red breast are important components of a display used to deter other robins from trespassing on an established territory. While the song proclaims “this is mine, stay away”, the red breast is used in more direct encounters. During a territorial dispute two robins will begin by singing at each other, with the territory owner attempting to sing from a higher perch than the intruder. This enables him to show off his red breast to maximum effect. If, for some reason, the territory holder finds himself positioned below the intruder he will throw his head back, again to maximise the amount of red breast on display. Such displays are usually sufficient to see-off the intruder but, if not, a ferocious fight may break out. The red breast is so important in this pattern of behaviours that a robin will even attack a bunch of red breast feathers. So, as the season of goodwill approaches – with the robin as its symbol – it is worth remembering that our beloved national bird has another side to its character.

Who rules the roost

Now that the birds are beginning to return to my bird feeders, I am reminded of the hierarchy that exists within this avian community. As tits, finches and the occasional house sparrows jostle for position at the feeders, it soon becomes clear who are the bullies in this outdoor dining room. Size plays a role; great tits oust blue tits from favoured perches and, in turn, the blue tits see off the smaller coal tits. In fact, the coal tits seem to prefer to sneak in, grab a sunflower heart and then beat a hasty retreat to eat their meal elsewhere; a sensible strategy for a bird at the bottom of the pecking order. Not so the greenfinches who dominate the feeders, each one seemingly picking through the hearts to select the plumpest seed. These aggressive birds force their way onto the perches and then turn noisily towards any birds that try to usurp them.

Even within a species there exists a clear hierarchy. Top of the tree, so to speak, are the adult males and it is to these that the females and younger individuals defer. The hierarchy is maintained by a series of threats and displays and only rarely does a dispute turn physical. From a biological perspective it makes sense for two individuals to settle their differences in a non-physical manner. In the harsh reality of the natural world, any injury that results from conflict has the potential to be life threatening and, with such high stakes, it is better to resolve a dispute without bloodshed. Birds and other animals use display to warn a potential opponent of their strengths. As such, an inferior individual can assess if it has bitten off more than it can chew by facing up to an individual that is likely to win a physical contest.

One of the interesting results of such dominance hierarchies is that individuals from lower down the pecking order may be forced to feed in circumstances that are less than ideal. Work carried out a number of years ago illustrates this point rather well. Researchers put up a number of bird feeders in different locations within a garden, with some feeders positioned in cover provided by thick shrubs and others placed out in the open, where the risk from sparrowhawk predation was much higher. The researchers then watched to find out how the feeders were used by great tits of different ages and sexes. While the dominant adult males chose to use those feeders placed by cover, younger individuals were forced to use those positioned in the open. The same thing will be going on in your garden so spend some time watching and all will be revealed.

Bedding down for the winter

The mild November weather had its effect on our wildlife, with very late sightings of certain butterfly species and reports of hedgehogs still on the go. Most hedgehogs build their winter nests during October and are safely tucked-up by mid-November. However, winter hibernation remains a flexible option for our hedgehogs and many will continue to remain active if conditions (both in terms of temperature and food availability) are suitable. It is a common misconception that hibernation is an extended form of sleep, during which the body is rested. Instead, it is a complex behaviour used to conserve energy during periods when the animal may be faced with highly unfavourable conditions.

Since keeping warm is an energetically expensive strategy during winter, the hibernating hedgehog abandons this, allowing its body temperature to fall. This controlled reduction in body temperature, typically brings the animal’s temperature down to within a couple of degrees of the ambient temperature. If the ambient temperature falls to dangerously low levels, which would cause the hedgehog to literally freeze to death, then the hibernating hedgehog will burn off more of its body fat to generate the heat needed to keep the body temperature at a safe level.  This controlled reduction in body temperature results in a fall in oxygen consumption, heart rate and breathing rate, together with a restriction in the amount of blood flowing to the major organs. While an active hedgehog may have a heart rate of 250 beats per minute (bpm) this falls to just 5bpm during hibernation. Research has shown that hedgehog hibernation is most efficient at 4ºC and one of the features that helps the hedgehog operate at around this temperature is the winter nest itself. Made predominantly from leaves, pushed up against a larger object, the nest provides protection from the worst of the winter weather. Temperatures within the nest typically remain between 1 and 5ºC, ideal for hibernation.

Hibernation is not continuous and a hedgehog will “wake-up” every 7-10 days. This takes between three and four hours and the hedgehog will normally remain within the nest for a short period before re-entering hibernation. Very occasionally, individuals will venture outside, perhaps to establish a new winter nest. These periods of arousal are energetically demanding, collectively accounting for 80% of the energy expended during the entire hibernation period. As such, they must be important for the hedgehog. Fat reserves fuel hibernation and these are laid down prior to hibernation and need to be sufficient to last the winter. Any young or undersized hedgehog weighing less than about 1lb (450g) is unlikely to survive more than the briefest period of winter weather, so should be rescued to a hedgehog rehabilitation centre.

Red signals danger for our crayfish

With the recent rain it is hardly surprising that the river is running so high. Still, it is a bright start to the day and I am optimistic that we will catch up with some crayfish, thanks to our trap and a punctured tin of cat food. We have just one native species of crayfish here in Britain, the white-clawed crayfish, but our chances of seeing this species are pretty slim on this stretch of river. Instead we are likely to see a good number of the larger signal crayfish, a menacing introduction from North America. While our native is a relatively small species, usually less than 10cm in length, the signal crayfish can reach 30cm. Bigger, aggressive and able to produce more young, this American interloper poses a real threat, something that is made worse by the fact that it can carry a virulent disease called crayfish plague. This disease seems to have little effect on the signal crayfish but it has contributed to drastic losses of native crayfish from many of our rivers.

A number of non-native crayfish species have been farmed here since the late 1970s and, perhaps inevitably, they have broken out and established themselves in the wild. Here they can occur in such incredible densities that their burrowing activities undermine river banks and flood defences. The threat from these alien crustaceans has now been recognised; the white-clawed crayfish has been listed as being globally threatened and research is underway to establish how the non-native species can be controlled and removed.

The Brecks Countryside Project is coordinating the research work being carried out locally. This work examines ways by which introduced species can be controlled through trapping; exploring different types of traps and bait, and looking to see if regular trapping has any impact on the size or structure of the crayfish population. The traps that we were on our way to examine the other morning were part of this project. Hauling them out of the water, it was clear that the signal crayfish were still very active at the site even this late in the year. The two traps held 29 crayfish, all signal. Each individual was sexed and measured, and then notes were made of the water temperature and flow rate. The mild conditions overnight had prompted the crayfish to venture out in search of food and the cat food would have proved highly attractive. This local scheme is a partnership between the Lark Angling & Preservation Society, the Brecks Countryside Project and The Environment Agency. Just coming to the end of its first year, the project has already generated some very useful information and it seems likely that more will follow next year.

A bad year for owls

It appears that 2006 has not been a very good year for our breeding owls. The latest information to have been published by the British Trust for Ornithology’s (BTO) Nest Record Scheme, suggests that many tawny owl nest sites were unoccupied this year. Tawny owls start nesting early in the year, with breeding territories established during the first part of the winter (which is why you may hear them calling now). A combination of food availability and weather conditions will determine if they then go on to breed. It appears that last winter there was simply not enough small mammal food around for many pairs to get into breeding condition and so they gave it a miss.

Barn owls, of which Norfolk holds a sizeable population, fared slightly better, with occupancy rates at monitored sites only down by a small amount. However, high levels of chick mortality and small brood sizes at fledging suggest that even these enigmatic birds were struggling to find sufficient food for their growing chicks. Even so, our barn owls fared somewhat better than those in the southwest of the country, where very few pairs managed to rear their broods of downy youngsters.

Such short-term failures in themselves are not necessarily going to have a long-term impact on the owl population, especially for a species like the barn owl which has tremendous reproductive potential. If 2007 proves to be a good year, with abundant food and good weather, then they should make up their losses. It is for this reason then, that the BTO monitors breeding success each year, extracting long-term patterns which may signal that a species is in difficulty. If a species shows a significant long-term decline in breeding success over many years then the BTO can issue an alert, warning the Government’s conservation advisors that there is a problem. The Nest Record Scheme’s current alert list contains 21 different species. Included in these are familiar birds like kestrel, which has shown a significant decline in brood size (the number of chicks in the nest) since 1990. Also included are the barn owl and bullfinch; the latter has, since 1990, experienced increased levels of nests failing at the egg stage. Could this be due to predation?

While the reasons for the patterns seen in individual species may differ from one species to another, there may also be underlying causes linked, perhaps, to global climate change (we know that many species are nesting earlier now than they did 20 years ago) or to changes in the nature of our countryside. As such, it is essential that we continue to monitor breeding success and to identify those species that need conservation action.

Woody's return

Back in June I wrote about the launch of a new survey, set up to establish the extent to which great spotted woodpeckers make use of gardens during the breeding season. The survey was a collaboration between the British Trust for Ornithology (BTO) and Radio 4’s “Shared Earth” programme (which is back on our airwaves for a second series today at 3pm).

The results of the survey have just been announced and they make very interesting reading. Reports were received from gardens across the country, including a number from here within Norfolk. Collectively, the contributions have enabled researchers at the BTO to build up a detailed picture of just how the woodpeckers change their use of gardens as the summer progresses. Early on in the season, from late June, adult woodpeckers begin to increase their use of garden feeding stations – arriving to tuck into peanuts and fats. The results suggest that males make greater use of this resource than females, something which almost certainly reflects the fact that females typically remain in the nest cavity during daylight hours, tending to their eggs or young chicks. During this period the male brings food to the female so she does not need to visit garden feeding stations. This pattern continues for several weeks and then, from early June, adults begin to arrive with youngsters in tow. These young great spotted woodpeckers can be separated from their parents by the red cap covering the top of their head and by the fact that the area of red under their tail is rather pale, seemingly appearing washed out. The adult male has a small patch of bright red at the back of his head and bright red underneath his tail. The female also has this patch of red under her tail but lacks the patch on the back of her head, all very useful features when it comes to working out just who is visiting your garden. Adults continued to arrive with their young over the following weeks but then left them to visit on their own. Having introduced their young to a suitable feeding opportunity their parenting was done.

Another aspect of the study looked at the extent to which these birds break into nestboxes containing broods of young tits. Many people do not realise thay the great spotted woodpecker is a predator of other birds’ nests but the study showed that many of those participants with a nestbox in their garden had experienced such predation. There are also reports of woodpeckers breaking into the mud nests of house martins to reach chicks.  It seems that the great spotted woodpecker is a resourceful bird, able to make the most of opportunities.

The tuneful Snipe

A crisp and bright November morning proved ideal for watching the flocks of duck and waders on the pools at Cley. Shoveler, wigeon and teal were busy bathing, while godwits and redshank probed for food, and gulls loafed about on the exposed mud. Only occasionally was this tranquil scene disturbed by the noisy arrival of another flock of brent geese or by the passing attentions of a hunting marsh harrier. The good light enabled me to spend some time studying one of the less obvious users of the pools, a snipe. These stunning little waders have dark, richly patterned plumage and are most often encountered by chance. Flushed from beneath your feet in some patch of wet meadow, they explode into the air with a hoarse call. A low zig-zag flight takes them away before the bird rises steeply up into the sky. Such brief views do not provide the time to appreciate the stunning plumage, so a bird feeding in the open at Cley is an opportunity to be savoured. It is worth noting that snipe sometimes perch on fence posts during spring and early summer – an even better opportunity to see them.

The most striking feature has to be the snipe’s bill. Long and straight (proportionally, it is the longest bill of any European bird), it is perfectly suited to a life spent probing the wettest margins of pools and the dampest of wet meadows. Here it feeds on earthworms and other soil-dwelling invertebrates. The loss of such habitats, through long-term drainage and changes in habitat management, has caused breeding populations to decline at an alarming rate. Norfolk’s breeding population has certainly declined, by 86% between 1992 and 2000 according to one set of figures, but the winter population is larger, swelled by the arrival of birds from further north and east.

The snipe, like its relative the woodcock, is known for its breeding display. Descending rapidly from a high flight, the bird produces a bizarre sound. Lasting for only a few seconds, the sound is best described as a fluting bleat. The noise itself is made by the air passing over the outer pair of tail feathers, which are held out away from the rest of the tail. The slightly opened wings help direct air over these tail feathers, which then vibrate to produce the sound. At the beginning of the last century there was much debate among British ornithologists as to how this sound was made. However, in 1912, Philip Manson Bahr, lecturing to the British Ornithologists’ Club, inserted two outer tail feathers into a cork, attached to a length of string. By whirling this around his head he was able to recreate the noise and halt the debate.

Heron drops by

We had a new bird in the garden last week - a grey heron. Although not the most popular of visitors for some, we were delighted to see such an impressive bird. The heron was perched on a wall; stiff and erect, it was alert to any danger but seemed uneasy within such urban surroundings. It must have been attracted by the presence of three ponds, one in each of the neighbouring gardens. At least two of these are free of fish, designed as they are with wildlife in mind, so it seemed unlikely that the heron would find them quite as attractive as they may have appeared from the air. Perhaps sensing this, the heron laboured up into the air after a few minutes to disappear behind neighbouring houses.

Herons have done well in recent years, their numbers increasing thanks to a run of mild winters. Cold winters, leading to frozen waterbodies, can spell disaster for herons, isolating them from their feeding grounds and increasing mortality levels within the population. The influence of winter weather on the heron population has been documented thanks to the British Trust for Ornithology’s annual Heronries Census. The study has been carried out annually since it was launched in 1928 by the late Max Nicholson, making it the longest running study of a bird population in Britain (and possibly the world). Although many heronries contain just a few nests, some can contain dozens or even hundreds. I used to live next door to a small heronry at Wolterton Park, to the north of Aylsham. Each spring, the ekk ekk ekk calls of the young herons could be heard, as they demanded food from their parents. The ground beneath the colony was splattered with droppings and pellets, the latter containing the coughed-up hard remains of unfortunate fish, eels, voles and amphibians.

Nowadays, I tend to see herons on the coastal marshes or along the river valleys well inland but, as my recent sighting shows, they will also visit garden ponds, a habit that can cause consternation for some. Discouraging herons from taking fish is not straightforward. A net covering the entire pond is the only truly effective deterrent.  Plastic herons, sold on the notion that having one by your pond will discourage a “real” heron from visiting, are useless since herons are not territorial and will often feed communally. Intersecting wires, placed a foot or so off the ground around the pond, may work because herons do not like stepping over objects. Of course, you could just add more cover within the pond itself, accept that you may lose the occasional fish, and enjoy the sight of such an impressive bird.

Harlequin poses threat to natives

Over the last few days I have spotted an increasing number of harlequin ladybirds. Normally I would be delighted to see a ladybird but the harlequin is not one of our native species. Instead, it is a potentially troublesome and invasive addition to our fauna, reaching our shores because of our own actions. Let me explain. The harlequin ladybird is a native of eastern Asia but it has been introduced to a number of countries as a biological control agent. Scientists, looking for an alternative to pesticides, have used the harlequin to control crop pests, such as aphids and scale insects, by introducing them into glasshouses, crops and even gardens. Unfortunately, as has been the case for a number of species used in this way, the harlequin has gone on to become a pest in its own right. It first established itself here in Britain in 2004, with individuals arriving from the Continent (where they had been introduced) thanks to their remarkable powers of dispersal or by gaining assistance in shipments of plants and other foodstuffs.

The harlequin ladybird is pretty catholic in its choice of habitats but does seem to favour deciduous trees like sycamore and maple. Here it feeds on aphids, scale insects, the eggs of various moths and a range of other insects. This species has a clear competitive advantage over most of our native ladybirds because it has a much greater breeding potential. The pre-adult stage lasts just 20 or so days (although this is temperature dependent) and, once they reach adulthood, the females can begin to lay eggs after just five days. This means that a single female can produce more than 1,000 eggs during her lifetime.

At the moment, the numbers of harlequins in Britain have not reached the pest proportions seen elsewhere in the world. In North America, many tens of thousands may overwinter in a single home and, given their tendency to bite, they are not the most welcome of lodgers. They are also a threat to our native species, especially when aphid numbers are low, as the species is likely to feed on other ladybirds and their larvae. Even wine production could be threatened. Harlequins are attracted to soft fruit, like grapes, and may occur in such numbers that they taint the resulting wine production with the alkaloid chemicals they carry to deter potential predators.

Fortunately, the Government has provided funding to the Harlequin Ladybird Survey Project (see www.harlequin-survey.org) to collate information on sightings and to undertake research to assess the level of the threat. It is also hoped to determine how the species may be controlled to prevent it becoming a pest. Let’s hope the research comes up with a solution.

Autumn storm forces Little Auks south

The start of November saw strong winds in the North Sea. Combined with the high tides, these brought flooding to parts of the east coast and a flight of little auks, pushed south from their more normal wintering haunts on the northern oceans. Reports of these tiny birds, no larger than a starling in size, came from along the north and east coasts of Norfolk. Most were seen passing close inshore but a few were found on coastal waterbodies or downed on the beach. One birdwatcher, who I met at a talk I was giving in Lowestoft, told me about one unfortunate individual taken by a great black-backed gull; the gull took several attempts before managing to swallow the auk whole.

The little auk is possibly one of the most numerous seabirds in the world, with a breeding population numbering many millions. The species breeds in the high arctic, nesting on rocky scree slopes on islands like Svalbard, Bear Island and Greenland. Individuals leave the breeding colonies in August, just as the sea ice is beginning to form. The birds then spend the entire winter at sea, where they form very large flocks which feed on small crustaceans and fish. These flocks can be found from the edge of the pack ice, south to the Gulf of Maine in the west and the northern North Sea in the east. Only when strong winds and sea conditions work against them do they get pushed further south to reach the Norfolk coast. In some years, very few little auks are seen off the coast of Norfolk – for example just seven were seen in 1994 – but in other years many thousands may be reported. The years when very large numbers are forced south are known as “wrecks” and it is during such events that individuals can be blown inland. In 1895, a huge “wreck” resulted in reports as far inland as Thetford and, across the county, some 250 were said to have been stuffed by taxidermists. Many of these storm-blown birds appear underweight and it is thought that poor feeding conditions may also drive the birds southwards.

I will never forget the first little auk that I saw, some 15 or so years ago. This wind-blown individual was swimming about in one of the channels that run at right angles to the east bank at Cley. The small, dumpy bird moved about as if it were a clockwork toy. The head and tail ends of similar shape reinforcing this image and suggesting that it might swim equally well backwards as forwards. Mind you, it is worth remembering that this tiny bird can survive a winter spent in the middle of the vast northern oceans.

Chattering from the reedbeds

A rather special warbler has recently put in an appearance on the Nunnery Lakes reserve in Thetford. I use the term “put in an appearance” rather loosely because the bird in question, a cetti’s warbler, has been rather elusive. Skulking within the thick vegetation, this particular individual has only revealed its presence through its characteristic song – a series of staccato notes and disyllabic alarm calls. These have an explosive quality and are far carrying – very useful when faced with a drab brown bird that prefers to remain low down within reed beds and damp willow carr.

The cetti’s warbler is the only British representative of a group of Asian warblers, known simply as the bush warblers. This particular species is a relatively recent addition to our breeding bird community. At the turn of the Nineteenth Century, cetti’s warbler was restricted, within Europe, to the shores of the Mediterranean. It then began a northwards range expansion that extended the breeding range to the Loire Basin in 1927, the Seine in 1932 and the Netherlands in 1968. The first confirmed breeding record from Britain was in 1973 and the species was first recorded in Norfolk in the same year, when an individual was found dead in the middle of Norwich city centre. This particular individual happened to be carrying a ring, showing that it had come from the newly established Belgian population. The bird is still held at the Castle Museum in Norwich.

A national survey carried out in 1996 put the British population at around 500 singing males, about 10% of which were recorded in Norfolk. Since then numbers have continued to increase and it is thought that the Norfolk population is now in excess of 200 singing males, most of which are located in and around the Broads at sites like Strumpshaw, Surlingham and into the Yare valley. This increase has only been possible because of the run of mild winters that we have been experiencing. Unlike other warblers that feed on insects, cetti’s warbler is a year-round resident and does not migrate to warmer climes in the winter. This means that it is extremely susceptible to periods of bad weather, when it is unable to find sufficient invertebrate food. We know, from past experience, that a particularly cold winter can dramatically reduce the numbers of cetti’s warblers in Britain. As such, the continued presence of this species within Norfolk, at the levels we have seen in recent years, is going to be very much dependent upon the pattern of future weather. Global climate change appears to be producing increasingly mild winters but it will only take one very cold winter to knock the population right back.

Where have all my birds gone?

Over recent weeks, increasing numbers of garden birdwatchers have contacted me to ask where all their birds have gone.  Familiar species like robin and blackbird have deserted gardens, leaving birdwatchers concerned that something untoward may be happening. Fortunately, this exodus is an annual event and one that forms part of the regular seasonal pattern of garden use. Autumn is a time of plenty, when Nature’s larder is packed full with wild fruits, seeds and nuts. As such, many birds will shun the food provided at garden feeding stations, in favour of beech mast, rose hips, berries and haws. The extent of this sudden switch in where to feed can be seen very clearly from the weekly records collected by the 16,000 BTO/CJ Garden BirdWatchers. Examination of the results for a species like blackbird (www.bto.org/gbw) shows an abrupt decline in the use of gardens, something which extends over several weeks. Once the supply of wild fruits is exhausted, the blackbirds return to gardens and the Garden BirdWatch reporting rate increases again.

You only have to wander out into the Norfolk countryside to see that many fruit or seed-producing plants have produced a bumper crop this year. Crops of acorns and beech mast are particularly large; that for beech being the largest since 2002. With such an abundance of food, seed-eating birds (such as coal tit, chaffinch, brambling, jay, nuthatch and woodpigeon) are likely to make very little use of garden feeding stations over the course of the winter months.  Work carried out by David Glue of the British Trust for Ornithology has demonstrated this link between seed availability and the use of gardens by coal tits.  During winter, when insect food is in short supply, coal tits switch to feeding on beech mast. When there is little beech mast available, more coal tits move into gardens to feed on peanuts and sunflower seeds. When there is a bumper crop of beech mast, they can remain within their favoured woodland habitats.

Many trees vary their production of seeds from one year to the next, using environmental cues to synchronise the size of the crop across large areas. This results in a run of years when seed crops are quite small, followed by the occasional year when they are very large. This large crop is known as a “masting” event and the strategy itself is designed to reduce the amount of seed taken by seed predators. If trees produced a similar crop each year then seed-predator populations would increase and the amount of seed eaten would be high. By having a series of small crops, followed by one big one, the trees effectively swamp the predators during the masting year, insuring that more seed survives to germinate.

Barking deer

From close by, the short, sharp-sounding bark of a muntjac deer unnerves the dogs. The deer has not heard our approach and can only be 20 metres or so away within the dense vegetation that borders this forest ride. More distant barks are ignored but the proximity of this one is enough to halt the dogs in their tracks. The series of single barks, each separated by a few seconds of silence, suggests that we are close to a female in season, possibly with a male in attendance; it is time to steer a different route and to leave these stocky little deer well-alone.

The dogs are certainly familiar with the muntjac that seem to do so well in and around Thetford Forest. The small hunched form of a muntjac is frequently seen crossing a forest ride and more distant barking is commonplace throughout the year.  The muntjac is an introduced species, originating from southeastern China, and first released at Woburn Park early in the Twentieth Century. Two different species were originally introduced, the Indian muntjac and the Chinese muntjac, but it is the Chinese muntjac that has become established. Standing about 48cm tall at the shoulder, these are small deer, short-legged and stocky in nature. The males have simple antlers which, in mature males, curve backwards and terminate in a hooked point. When alarmed, the short tail is raised and held vertically, displaying the conspicuous white underside – a useful identification feature. The very small hoofprints, with those of the rear feet registering upon those made by the forefeet, are also characteristic.

Muntjac breed throughout the year and young can be born in any month. After birth the female comes into season and will be pursued by a male for some time prior to mating. Each male utilises a home range that encompasses those of several females. Ownership of an area is signalled through scent marking, a behaviour utilised by many other mammal species for social communication. The males, and in particular dominant males, use scent marking to a greater degree than the females. In front of each eye is a large scent gland, which is frequently opened and sometimes everted (resembling a black grape) during courtship. Frontal glands, positioned on the forehead, are used to mark the ground and glands between the digits of the hind foot leave scent wherever the animal wanders. Such communication helps to signal the social status of individual males and is often enough to deflect potential aggressive encounters. These do happen on occasion and may sometimes be directed towards other species seen as a threat, including foxes and dogs – another good reason for me to steer my dogs away from the courting couple.

Moorhens enjoy good breeding season

There seem to be plenty of moorhens about on the river at the moment. The ratio of adults to youngsters suggests that it has been a particularly good breeding season and this bodes well for the winter ahead. It also suggests that the mink that had previously been present on this stretch have now gone, thanks to a combination of trapping and the return of the otters. There is something very comical about the moorhen. When seen out of water, the charcoal grey body appears to have been glued onto the thick yellow-green legs of a larger bird. The moorhen seems to emphasise this, as if unaware of someone else’s practical joke, by walking with a sprightly high-stepping gait. Alongside this there is the regular flicking of the short tail, like a nervous twitch, which again adds to a rather unusual demeanour.

Despite their comedic appearance, moorhens are rather interesting birds. For example, the moorhen holds the dubious distinction of being one of the first birds to fall victim to a firearm within Norfolk. Two great Norfolk nature writers, Gurney and Stevenson, both cite a record of one being “kylled wt the gun” in the mid-1500s. Indeed, the moorhen has sometimes featured as a bird for the table (and still does in other parts of Europe).  The dark meat was used in some rural parts to supplement the limited rations available during World War Two. Interestingly, some authors suggest that the bird was skinned rather than plucked prior to cooking. Certainly the moorhen is a popular component in the diet of a number of predators and the species appears especially vulnerable when nesting.

Although most of our resident moorhens remain on their breeding territories throughout the year, they are forced to move during periods of severe winter weather, when waterbodies freeze over and food becomes hard to find. Moorhens from breeding populations in Denmark, Sweden and the Netherlands are known to winter here and large numbers may regularly gather at favoured sites. Back in the mid-1990s we used to have a couple of dozen moorhens gather at the bottom of The Nunnery lawn in Thetford. These birds would feed on the edge of the lawn or venture into the wet woodland which separated the grounds from the river. We made an effort to trap and ring the birds – a job which involved careful handling because of the extremely sharp claws sported by these birds – and were rewarded several months later by the report of one that had made its way to Shetland. Other individuals (not ringed by us) have been reported from Denmark, Sweden and the Low Countries. There is certainly more to this bird than you might imagine.

Hornets aplenty

Just off my regular route to work, there is a large hollow tree by the river. The cavity is at ground level, large enough to accommodate those of slender build and heavily charred thanks to the fondness of the local children for all things pyrotechnic. At the back of the cavity, the pale off-white form of a large hornets nest provides a striking contrast to the charcoal black trunk. The nest extends down, marked with horizontal bands of cream, brown, yellow and white, that delineate the many layers of chewed wood pulp that have been processed by the hornets and formed into the paper soft structure. Even now the nest is active, with up to a dozen hornets around its entrance at any one time. Each magnificent individual is close on three centimetres in length, with a warm cinnamon-brown tinge to the wings, pronotum and legs. These are the largest and most majestic of our eight species of social wasp. In my experience they are also the most docile, being extremely good-natured around the nest. The presence of the nest explains the large number of hornet sightings along the river over recent weeks, as workers strike out in search of food.

At this time of the year such a nest could harbour several hundred individuals. Certainly, the steady stream of returning individuals and departures of others suggests as much. Most navigate between me and the entrance to the cavity, as I try to position my camera so as to get a shot of the nest. Others, just the odd one here and there, give me the once over, perhaps curious as to the object that now blocks their usual approach to the nest. It is amazing to be so close to such a large nest; those I have seen in previous years have tended to be far smaller.

The hornet is a rather uncommon and sometimes localised species, though widely distributed across the southern half of Britain. Most nests are, like this one, located in tree cavities, although they may be found within buildings or, occasionally, in cavities beneath the ground’s surface. Like the other social wasps, the hornet has an image problem and has become one of the most feared of British insects. This is a real shame, not least because it preys on a wide range of insects that are typically classed as garden pests. They may occasionally become a nuisance by preying on honeybees or by ring barking lilac shoots to exploit the sap but, left alone, they are one of the good guys. The question of just how long this nest will be left alone remains to be seen. With a footpath close by, the cavity is tempting for adventurous children.

Become a plover lover

Mixed flocks of lapwing and golden plover will be a familiar sight to those who venture into the Norfolk countryside at this time of the year. On dull autumn days, the hunched silhouettes of these medium-sized wading birds can be seen on freshly ploughed fields or areas cleared of sugar beet. Both species make less extensive use of mudflats than other wading birds and, as such, they can turn up almost anywhere across our largely agricultural county. While some of the lapwing will be birds that have bred locally during the summer, perhaps at Holkham or within the Brecks, most will be drawn from breeding populations elsewhere, including Fennoscandia and the Low Countries. All of the golden plover will be winter visitors – the species does not breed in Norfolk – drawn from upland areas spread across northern Europe.

Because the wintering populations of these two species make use of inland agricultural habitats they are not well-monitored through existing monitoring schemes, such as the Wetland Bird Survey (WeBS); paradoxically, though, Breydon Water supports an internationally important population of lapwing. The use of inland habitats means that the size of their wintering populations has to be determined through a special wintering plover survey. This is organised by the British Trust for Ornithology (BTO) and, with concerns of a potential population decline and a suggested shift in wintering range, the latest survey is taking place this winter. Most of our wintering lapwing arrive between late September and the end of November, with peak numbers of golden plover noted in November. Later into the winter, birds may become more mobile as freezing temperatures force them to move south or west to find areas free from frost, where they can feed. Both species prefer to feed on areas of permanent pasture, rich in earthworms, a habitat that is scarce within Norfolk. Instead they make use of winter cereals, oil seed rape and sugar beet stubbles, feeding at night on beetles and earthworms.

Sizeable mixed flocks can literally ‘carpet’ fields but smaller flocks, of 50 or so birds, often go unnoticed. If you are out and about in the countryside this month, make an effort to scan the fields for these two plovers or offer to take on one of the BTO’s survey squares. While the bulk of the survey work will be carried out by BTO volunteers, visiting the randomly selected survey squares, information is also needed from other areas. Records of lapwings or golden plovers seen anywhere within the county are especially welcome and can be submitted on a casual records form. Copies of the form can be obtained by downloading it from www.bto.org/goto/winter-plovers or by phoning the BTO on 01842-750050.

From blackberries to airmiles

Despite the fact that we enjoyed a couple of summer-like days earlier this week, there is no escaping the fact that autumn is upon us. The telltale signs are there; browning of the bracken, the scent of mushrooms in the woods and a change in bird behaviour. For many birds, the time has arrived to start out on an autumn migration that will take them south from our shores, into Europe and beyond into the dark heart of Africa. In most species, this is not a journey upon which they can embark without first making some important preparations. Flight requires fuel and small birds, like migrant warblers, must take on board the fuel necessary for at least part of the journey, perhaps stopping en route to top up their reserves. Only those that can feed on the wing, such as swallows and swifts, can avoid having to lay down large reserves of fat in advance.

Many of our small migratory birds will add to their fat reserves very quickly, perhaps adding between 10 and 13pc of their body weight each day during this period of fattening. Some of the increase comes from eating more food, with birds making the most of autumn’s bounty. At the same time, many species make better use of the food they ingest, either through changes in their metabolism or by selecting foods that are easy to digest. Many fruits are ideal; low in fibre, abundant at this time of year and easy to digest, they also tend to be rich in sugars (which help in the deposition of fat). Hedgerow shrubs heavy with berries will be well-attended by warblers and thrushes over the coming weeks. Other species, such as the sedge warbler, feed selectively on aphids, a behaviour that may be related to the relatively high sugar content of these invertebrates.

Bird ringers catching birds at this time of the year often comment on just how fat some of these small birds can become. While a species like a garden warbler would normally weigh about 17g, just prior to migration it may reach 34g, raising the question of how it manages to get off the ground. This highlights the trade-off that a migrating bird has to make. The more fuel it takes on board, the heavier it becomes and the slower it flies (making it a target for predators). There must be an ideal fuel load for the journey, something that will depend on how far the bird has to go, whether it can refuel en route and how likely it is to meet a predator. It is a good job that things are less complicated when we go on holiday!

One for sorrow, two for joy

The old saying begins “One for sorrow, two for joy” but the other morning I find myself wondering what would seven magpies bring. The seven in question were gathered in the middle of the road around the corpse of a brown hare, presumably killed by a passing car. They took to the air as I drove towards them; young birds, their tails not yet fully developed, with at least one adult bird alongside them. Perhaps they were learning the ropes, discovering the easy meals to be had at this time of the year on Norfolk’s roads.

Despite striking plumage and resourceful nature, the magpie is often viewed with suspicion or even outright loathing. It has long been said that the magpie has a drop of the Devil’s blood in it. This is not the only religious association. The magpie was the one bird that refused to enter Noah’s ark, choosing instead to perch on its roof and chatter and swear at the drowning of the land. To add to this, Christian tradition has it that the magpie did not go into mourning at the time of the crucifixion. The habit of caching food for use in more difficult times, a strategy adopted by a number of bird and mammal species, has given the magpie the reputation of being a thief. This is perhaps most famously celebrated by Rossini’s opera ‘La Gazza Ladra’ – ‘The Thieving Magpie’.

You have to have respect for the magpie. An incredibly adaptable bird, it is able to feed on a very wide range of foodstuffs and has managed to exploit all sorts of opportunities. The magpie was one of the first species to peck open foil-covered milk bottles to reach the cream inside, a behaviour that extended to raiding egg boxes left alongside. However, the habit of raiding the nests of other birds brings an angry response from some quarters. While such behaviour can ruin breeding attempts, there is no evidence that this act of predation has had any effect on long-term changes in songbird populations, despite several scientific studies looking hard at this very issue. Our long history of rearing game no doubt contributes to a collective anger directed at the magpie, with persecution of this species fortunately less intense that it once was.

So what of the rhyme? What would seven magpies bring? There are many variants of the rhyme but the oldest version that I can find (and the one I use here) dates from 1750. It runs “One for sorrow, two for joy, three for a girl and four for a boy. Five for silver, six for gold, seven for a secret never to be told.” Don’t tell anyone but I rather like magpies.

Celebrating Norfolk's moths

There is something deeply rewarding about running a moth trap. The sense of anticipation that grips me each morning, as I come to empty the trap of its nocturnal visitors, reminds me of being a child on Christmas Day, eager to open presents waiting under the tree. Perhaps, in some way, catching moths rekindles the ancient instincts of Man the hunter. More likely though, it reflects a need to discover, identify and “collect” (in this case photograph).

Running a moth trap requires little effort on my part. The trap itself is a wooden box, partly covered with two perspex sheets, above which a bright mercury vapour bulb is placed. Set at dusk, the trap does its work through the hours of dark, leaving me to rise at dawn and check the contents. Moths are attracted by the light and, flying into the bulb, drop into the box below. Here they seek shelter amid the pile of old egg boxes, remaining dormant until my arrival. Unless you have ever seen a moth trap in operation, or rather the results of its work, you will have no idea of just how many beautiful and diverse moths there are in Britain, both in terms of species (about 30 for every species of butterfly) and number of individuals. Many of our moths are more beautiful in appearance than their diurnal cousins but because they are largely nocturnal, they are under-appreciated.

All that may change if, as seems likely, increasing numbers of people continue to take up moth trapping. This coming weekend sees an event that is sure to encourage more people to take up this fascinating hobby. Saturday 23^rd is National Moth Night – a celebration of Britain’s moths and of moth recording in general. The organisers, Butterfly Conservation and the publishers of Atropos (a journal for moth enthusiasts), hope that people across the country will either visit planned moth events or set up their own simple moth trap (a bright light shone on a white sheet). The timing of National Moth Night differs from year to year, to vary the range of species encountered – moths have defined periods when they are on the wing. While September may not be the best month for catching large numbers of moths, it offers some rather colourful species, particularly migrants from across the channel. The results collected by participants are pooled into Britain’s largest survey of which species are flying and where, highlighting the conservation value of trapping.  Judging by the sorts of species being reported across Norfolk at the moment, it should prove to be a very interesting event. To get involved yourself, why not grab an old sheet, a bright torch and visit http://www.nationalmothnight.info to find out more.

Disease outbreak hits finches

I have received an increasing number of calls over recent weeks from garden birdwatchers concerned at the appearance of dead and dying finches. In most instances these reports have involved greenfinches and chaffinches but there have also been occasional reports involving other species. This is not the time of the year when we would normally see birds dying from common diseases like salmonella and e-coli (these are normally seen in late winter), which suggests a different source. Thanks to the efforts of researchers working on the Garden Bird Health initiative, we have discovered that the disease involved is trichomonosis. This disease is caused by a parasite and it has been documented in a range of bird species, most commonly in doves and pigeons (where it is more commonly known as ‘canker’). The disease was first recognised in finches in Britain last summer, when a small outbreak was noted but this summer the outbreak seems to be that much larger and this has caused some concern.

Individual birds showing signs of the disease appear lethargic, fluffed up and reluctant to move away from feeding stations. They may have difficulty swallowing and may drool saliva or regurgitate food, something which can cause the feathers around the bill to become wet. Although in captivity the disease can be treated, it is virtually impossible to treat wild birds with an effective dose of medication. This means that prevention is the only practical option and garden birdwatchers should aim to reduce the risk of disease transmission between birds by adopting sensible hygiene practices. These include keeping bird feeders and bird tables clean (with a disinfectant or detergent) and by insuring that clean, fresh water is available each day, provided in vessels that have been thoroughly cleaned. It has been suggested that you should stop feeding altogether if you find any sick or dying birds but I feel that it is better to feed birds at a clean feeding station than force them to move on and potentially feed elsewhere where no hygiene measures are in place.

Most of the reports that I have received so far have come from western and central England but we should be alert here, in Norfolk, to the possibility that the disease might arrive. The parasite itself cannot survive for long outside of the body and it appears to be transmitted through salival contamination of food and water. This may be why it has been more widespread this summer – with the dry conditions reducing the availability of drinking pools and forcing more birds to congregate at those which remain.  More information on the disease and on sensible hygiene measures can be obtained from the British Trust for Ornithology and UFAW.

Dragonfly gives me the once over

It is quite a strange feeling to be given the once over by a dragonfly. On one very warm afternoon last week this is exactly what happened. A dragonfly, about seven centimetres in length, approached me with a very direct flight and hovered just in front of my face. After a brief moment it adjusted its position, viewing me from a slightly different angle before turning and moving away to continue its patrol. As it turned I could see the paired spots, one large pair on each segment of the elongated abdomen. Most of the spots were a pale leaf green in colour. Those on the last three segments were pale blue and the last two pairs of these were each fused into a single larger spot, all characteristic features of a male southern hawker dragonfly. This is an inquisitive species that patrols low down around its favoured small, shaded pools and ponds. As such, it is often common in wooded areas and in urban gardens, where cats frequently catch it.

This was not the only species of hawker that I have seen in recent days. The similar, though somewhat smaller, migrant hawker has been much in evidence, patrolling over local ponds and getting caught in our mist nets, used to catch swallows on the local fen. The male migrant hawker also sports paired spots, though his are pale blue along the full length of the abdomen and all remain unfused. A yellow wedge, shaped like a golf tee, appears in the middle of the second abdominal segment, a feature absent in our other hawkers and useful when dragonfly watching. Migrant hawkers appear to be less inquisitive than their larger relative, patrolling low only around breeding ponds and preferring to search for food up along the edge of trees and hedgerows. As its name suggests, the migrant hawker is, to some extent, a summer visitor, with large numbers reinforcing our resident breeding population.

These two ‘blue-green’ hawkers are joined in Britain by another ‘blue-green’ species: the common hawker, which, despite its name, is anything but common within Norfolk, being restricted to a few localised sites in the east of the county. There are also two brown-coloured hawkers to be found in Norfolk, one of which, the Norfolk Hawker, is not found anywhere else in Britain. With its brilliant green eyes, this striking beast is well worth looking for in spring around the Broads. Any brown-coloured hawkers seen on the wing at this time of the year will be a brown hawker, a more widespread species. A number of related species may turn up in the county as vagrants and, with global warming, some of these may yet become established.

Icons of the northern summer

Over the past few weeks I have spent a number of very pleasant evenings out on the fen. Working with a team of bird ringers, I have been involved in an important international project tracking the autumn swallow migration. The British Trust for Ornithology’s ‘Swallow Roost Project’ sets out to assess the pre-migratory strategies of different populations of swallows by collaborating with teams of bird ringers in other parts of Europe. Our own efforts on the fen over the last few years have varied in their success. On some evenings the swallows play ball and fill our nets. On other evenings, the nets remain empty.

The swallows come into roost just before dusk, favouring the edge of a reedbed where, with water beneath them, they feel safe from predators. Small parties of swallows, moving through the river valley, are drawn down to the reedbed by the swallow calls emanating from our tape-lures but it requires knowledge of where they prefer to roost to make sure that we place our nets correctly. If we get it right then the birds are caught in the nets as they pass low over the reeds. Once all the birds have been safely removed from the nets, we begin the process of ringing the birds and taking the all-important measurements that will help us establish how these long-distance travels prepare for their epic journey.  After we have processed each swallow it is placed in a roosting box where it will spend the night, before being released early the next morning. Preliminary examination of the information that has been collected suggests that British swallows, in contrast to many other small migratory birds, do not put on much weight before they depart our shores. Instead, they appear to fatten up on the Continent before making the journey across the Mediterranean, into Africa and across the great expanse of the Sahara.

Sometimes our efforts do not succeed because the swallows choose to roost in a different part of the reedbed. On other occasions, the presence of a hobby may frighten the swallows off, such that they choose to roost somewhere else entirely. The hobby is a superbly adapted bird of prey, with an explosive burst of speed and well-able to catch a swallow. As the season progresses, hobbies seem to appear more frequently and the number of swallows using the roost becomes more erratic. Just last week we had at least two hobbies over the fen and the 60 or so swallows remained high, refusing to venture down into the reedbed roost. With the hobbies present the swallows eventually moved off elsewhere. Even on those evenings when we fail in our task, there is always plenty to see, making the effort worthwhile.

Modern parenting in Norfolk

This time last week I was at the Birdwatching Fair at Rutland Water, manning a stand promoting the BTO Garden BirdWatch. While the weekend itself was very interesting, it did mean that I missed the largest flock of dotterel to have visited Norfolk in nearly fifty years. This attractive wader breeds high up in the mountains of Scandinavia, Scotland and Russia. As such, it remains a scarce visitor to Norfolk, passing through in small numbers during its spring and autumn migrations. At least two-dozen of these delightful birds, and possibly as many as three-dozen, spent much of the weekend frequenting fields near Choseley Barns, which sit on the hill inland of Titchwell.

With smart grey upperparts, a white band across the chest and a rufous belly, a dotterel in breeding plumage is quite a sight. Remarkably (for a bird) the female dotterel is more brightly coloured than her mate, a trait that hints at an unusual approach to courtship and parenting roles. It is the female dotterel that initiates courtship, performing song flights to attract a mate. Once courtship is complete, the female will usually leave the male to incubate the eggs and rear the chicks on his own, while she is free to search for another mate. The roles of the two parents are determined by the different levels of investment in the reproductive attempt. Since eggs are energetically costly to produce, and sperm is cheap, it is unusual for a female bird to have the upper hand in determining the parenting roles. In this case, however, the female seems to have overcome any handicap.

The dotterel used to be more numerous when on passage through the county. Stevenson, writing in the late 1800s, noted that the species used to be so numerous that there was considerable profit in hunting it. Within Norfolk, the birds were netted, providing a great delicacy for the table. Some authors considered that the dotterel was easy to trap, a fact that may have had some bearing on its Latin name of “morinella”, which means “little fool”. The vernacular name itself shares a linguistic root with “dotard” again suggesting that the bird was rather stupid.

The general pattern within Norfolk is for more dotterel to be seen during spring migration than during the autumn one but, interestingly, the largest groups tend to be encountered during the autumn. A record 47 were seen together at Terrington Marsh on 20^th August 1959, while the largest group seen in more recent years was 17 near Docking on 26^th August 1996. These small groups of dotterel are known as “trips”. It’s just a shame that I couldn’t make the trip back from Rutland in time to see them last weekend.

Rare caterpillar found at Holkham

The National Nature Reserve at Holkham is an excellent place to visit in search of wildlife. The combination of habitats (such as dunes, inter-tidal sands, grazing marsh and pine woodland) allows the development of many very different communities of animals and plants. During the winter months, visiting shore larks and snow buntings can be seen on the saltings, while huge flocks of geese crowd onto the grazing marsh. The summer warmth brings natterjack toads, spotted flycatchers and a whole host of buzzing, chirring and clicking insects. The heat also attracts the tourists and Lady Anne’s Drive soon hosts two long lines of parked cars, the sun on their windscreens creating the illusion of two great glasshouses stretching out towards the pines. Fortunately, Holkham is a large site and, with the lure of the sea, it is very easy to leave the crowds behind and lose yourself in the solitude that the reserve has to offer.

Bedstraw Hawk-moth, Holkham

Just the other weekend I visited Holkham with two friends whom I had not seen in a long while. It was the perfect venue for a gentle walk and provided an ideal opportunity to catch up on each other’s news. Skirting west alongside the landward edge of the pines, we soon reached the George Washington Hide and followed the boardwalk out onto the dunes. Common blue butterflies were on the wing in the shelter that the dunes provided, and alongside these were graylings, dark green fritillaries and dozens of gatekeepers. Scanning the ground for beetles and other invertebrates soon turned up our most interesting find of the day – a bedstraw hawkmoth caterpillar. This pale, straw-coloured caterpillar was a sizeable beast – the length and thickness of your middle finger. Complete with a series of ‘eye-spots’ along the flank and a red ‘horn’ on the rear end, I recognised it as a hawkmoth caterpillar, but one that I had not seen before. Photographs were duly taken and, once home, these were compared with various illustrations before my tentative identification was confirmed by a number of experts.

The bedstraw hawkmoth is a migrant species, albeit a fairly regular one, and so was not something that I would necessarily have expected to encounter as a caterpillar. Most records tend to come from the eastern counties and, in particular, from coastal localities. Adults usually occur between May and August and may be taken at light traps but the caterpillars themselves tend to be found from July to September. They feed on various bedstraws and willowherbs before overwintering just below the surface of the soil. At various times in the past, temporary populations of this moth have become established in North Norfolk. This latest record may suggest that one such population exists today at Holkham.

House MArtins may linger

The familiar house martin, with its blue-black upperparts, crisp white underparts and white rump, has had something of a mixed summer. The extended period of drought will have made it difficult for individuals to find the mud needed to build or repair nests but, at the same time, the summer warmth has helped to support an abundance of aerial prey. Many house martin pairs will be on, or have finished, their second broods and it will not be long before some begin to depart our shores. Others may be further behind and a few, well ahead of the game, will have managed to squeeze in a third brood. The recent run of cold wet weather will have limited chick growth rates, extending the development time well beyond the usual 16-22 days. This means that some youngsters may remain in the nest through into the middle of October. The presence of such lingerers often prompts phone calls to my office from worried homeowners, fearful that “their” house martins will be unable to make the journey south. Such fears are usually unfounded unless the weather deteriorates and food becomes scarce. I suppose that this highlights our attachment to these delightful birds that have chosen to nest alongside us. Although the majority of nests are now on man-made structures, especially under the eaves of houses or under bridges, house martins would have once nested in cliff faces, like those at Hunstanton.

Not everyone welcomes nesting house martins and the mess that accumulates below the nest, but it is worth remembering just how far these transequatorial migrants have come and the amount of effort they have put into building their nests. Each nest takes about 10 days to build and is made up of over 1,000 beak-sized pellets of mud. On occasion, having just completed their nest, a pair will find themselves evicted by house sparrows. These more dominant birds muscle in and take over what is, for them, an ideal nest site.

Despite the apparent familiarity, we actually know surprisingly little about house martins. Although some individuals roost within the nest during the breeding period, it is thought that most roost at altitude on the wing (like swifts). We know even less about what happens to these birds during the winter months. Even though some 300,000 have been ringed in Britain, only one has been recovered in Africa, south of the Sahara, although local reports suggest that this is where they winter. Researchers believe that house martins spend the winter months feeding on the aerial insects that gather above the rainforest canopy. Since very few people live in such areas, perhaps it is no surprise that more individuals have not been found.

Audit of our bird populations

Last weekend saw the launch of “The State of the UK’s Birds 2005”; a now regular publication charting the changing fortunes of our bird populations. Published by the British Trust for Ornithology, RSPB and the Wildfowl and Wetlands Trust, in association with the four Country Agencies, the report provides a very valuable measure of how our birds are fairing. Knowing that a species is in decline can help to trigger appropriate research and plan effective conservation action. Similarly, evidence that a species has begun to recover from a previous decline is a valuable yardstick by which the success of conservation work can be measured.

The information presented in the most recent report comes from a wide range of surveys, some covering multiple species, others targeted at single species or particular sites. While figures for individual species provide the best level of detail for conservation efforts, they can also be used collectively to stimulate appropriate policies for Government. One way in which such an approach has been adopted is through the use of indicators, such as the “farmland bird indicator” which summarises what has been happening to farmland birds as a whole. This particular indicator demonstrates that, as a group, farmland birds underwent a period of sustained decline during the 1970s and 1980s, from which they have yet to recover. Government sees indicators as a useful tool for communicating the state of the natural environment and for measuring the success of Government policy. However, some researchers feel that they are of limited value, not least because they may hide all-important differences between individual species. Nevertheless, thanks to work carried out at the British Trust for Ornithology, the UK has led the way in developing these useful tools, demonstrating the role they can play in conservation.

One underlying message within the report was the essential role that volunteers play in collecting the information upon which much of our understanding is based. The report presents long-term information for many widespread species, monitored by volunteers who give up time each year to go out into the field and collect information in a standardised manner. Without these volunteers, we simply would not have the information that is needed. A similar message emerged from the recent run of programmes on BBC Radio 4 looking at “citizen science”. This American term is used to describe the way in which ordinary “citizens” participate as volunteers in projects organised by scientists to collect information at a scale that could not be achieved with paid professionals. If you are out in the countryside, collecting information on plants, bugs, birds or bees, then you are doing your bit of citizen science and helping the nation’s conservationists and researchers.