On the move

There is a bit more wind than I had expected from the forecast but at least there is some warmth in the sun’s rays this morning. It is good to be on the east coast, with sand beneath my feet and some coastal bushes and scrubby cover to search for migrant birds. Over recent days there have been a good few migrants here, including a number that no longer breed in the county but merely pass through on passage. There’s a chance of a vagrant warbler or perhaps a passing shrike. Out on the short-turf of the now vegetated dunes there is even an outside chance of a wryneck.

Today, however, fails to turn up anything rare – not that it really matters. I am not here to tick off something new or to add some rarity to a list. I am here, in this beautiful place, to watch birds and immerse myself within the landscape. What I like about this particular stretch of coast is that there is plenty of scrubby elder cover and a great scramble of bramble and bindweed, all of which provide feeding opportunities for birds and insects alike. Such patches require patient watching because those birds that are present can remain out of sight for long periods. The gentle pebble-tapping alarm call of blackcap reveals the bird’s presence long before it emerges from the bramble in which it has been sat, agitated by the passing dog-walkers.

Over the course of a couple of hours working a few dozen metres of low and crumbling cliff, I am treated to whitethroat, chiffchaff, willow warbler and pied flycatcher; migrants one and all, journeying south. Overhead, the chattering calls of swallow and martin signal other birds on the move, while a few dragonflies patrol lower down, the buzz of their wings catching my attention as the occasional individual steers close to my head and away. Large white butterflies dance around the bramble alongside smaller numbers of comma and red admiral, the latter so beautifully marked that they cannot have been on the wing that long. There is a real sense of movement and it is truly energising to see the ways in which this little stretch of coast is being used.

Small whites on the move

It wasn’t the sort of sight that leapt out at you, a series of small white shapes fluttering across the salt-marsh, but with a bit of studied thought it became clear that we were witnessing an ‘event’. The white shapes were small white butterflies and the unending procession of individuals, moving from west to east across the marsh, implied that these were not simple random wanderings; these flights were a population on the move, an autumn migration on a grand scale.

The small white is well known for its powers of dispersal. It is a wanderer, whose loose and open populations are to be found across virtually the whole of Britain and Ireland. The second brood, which tends to emerge in late June or early July, is much larger than the first, which may suggest that its numbers are boosted by the arrival of immigrants from the Continent. Later in the year comes the suggestion of a return movement, the butterflies moving south and east as autumn begins her tenancy of our countryside.

There has been some debate around the extent of migratory movements made by this species. That large numbers may arrive here from the Continent has been well documented. Writing in 1846, the Reverend Morris (a renowned lepidopterist) reported a case where a cloud of small white butterflies passed over a continental steamer and obscured the sun. Upon making landfall in England the great cloud of butterflies broke up and dispersed inland. Evidence for autumn movements is less striking but many lepidopterists will tell you that it does indeed occur. Work elsewhere in Europe, looking at the movements made by other species of butterfly, has revealed that complex migratory movements do take place, the different stages of the movements occurring within the different generations of the butterflies.

Whatever the underlying reason, it was clear to us that a great many dozens of these insects crossed out path that morning, all heading in the same direction and all flying into the prevailing wind. The total number of individuals involved must have been staggering, so great the area of coastal salt and grazing marsh over which they were passing. Some could even be seen passing offshore as we scanned for seabirds.

Nocturnal movements

There have been some nights recently when, taking the dogs out just before bed, I have heard the calls of golden plover and lapwing from high above me in the dark winter sky. These are birds on the move, perhaps local flocks moving between feeding sites within Breckland or recent arrivals from the Continent, pushed west by changing weather conditions. Such movements are common at this time of the year but they largely go unnoticed as birds pass overhead in the darkness while we are, for the most part, tucked up in the warmth of our homes.

Evidence of the range of species on the move comes not only from the occasional calls heard and noted down by birdwatchers, but also from the corpses that are sometimes found beneath office block windows in our urban centres. It is thought that some of these nocturnal migrants collide with lit buildings, perhaps even drawn to the light of illuminated office windows. Other individuals may be taken by urban peregrines, hunting at night with the aid of urban light pollution. Such behaviour has been little studied here in the UK but a growing interest in cities like Bristol is beginning to reveal the extent of the behaviour and the range of species taken. As BBC Winterwatch revealed, the Bristol peregrines have taken woodcock, snipe and even little grebe.

Many other birds are on the move at the moment, though not always at night. Changing weather conditions across large parts of continental Europe, with temperatures falling and waterbodies freezing over, may see an influx of waterbirds, including geese and swans, into the UK. The warming influence of the Gulf Stream means that Britain and Ireland present more favourable wintering conditions than those of the near Continent and east towards Russia. A flight of swans over Thetford just the other may have been such an arrival.

Of course, some birds are leaving our shores at the same time. Wintering blackbirds and other thrushes may move further south or southwest with the arrival of snow. Redwings, in particular, find cold conditions challenging and so tend to be very mobile. Some of those to have wintered here may move some way south into Iberia, perhaps even reaching the Mediterranean. The waxwings that have been such a feature of this winter are also very mobile, although in this case the movements are made in response to the availability of (or lack of) the suitable berry crops on which they depend.

If you can spare time to wrap up warm and stand in your garden on a still, clear night then you too might be treated to the soft calls of birds, passing overhead in the dark of night.

Winds from the east

The last week of September delivered a feast of migrant birds for east coast birdwatchers. With winds from the east, coupled with cloudy and wet weather hanging over the coast, conditions were ideally suited to produce an autumn ‘fall’ of small birds to coastal hedgerows and shelterbelts. Good numbers of redstarts and pied flycatchers were widely reported, together with less common birds like yellow-browed warbler, red-breasted flycatcher and Richard’s pipit.

One of the real joys of birdwatching the Norfolk coast under such conditions is not knowing what you might find while out working a favoured patch of habitat. There is a chance of something unusual, something unexpected and, just occasionally, something rather special. It is just a chance mind you, but the more time that you spend out there the better are the odds of something really good turning up.

It is interesting to think about the birdwatcher’s perception of what is a good bird. While for some it is all about rarity, for others it is the challenge of securing the identification of a bird that is notoriously tricky. For me it is about the sense of place, the bird in the landscape and part of a wider experience. Looking back through my notebooks for this time of the year underlines this. Notes on a barred warbler I found at Kelling, for example, are mixed in with mention of late bush-crickets and the antics of some young common rats, clambering about in the bramble to get at the berries. It is not so much the bird that is the focus but the wider experience.

There are barred warblers about again this autumn and a chance that I might stumble across one, just as I might see young rats or something else, a chance encounter providing a lasting memory. Just being out provides the space to think and relax, to sense your place as the seasons shift and nature responds. Given how much time is spent in an office or in front of a computer, I believe that these moments spent outside have an important role, keeping us rooted in the natural world, reminding us that we are part of something more dynamic and responsive. Computers and televisions direct our gaze to a single point and narrow our horizons but being outside frees us from this, it allows us to gaze around, to be saturated by sounds and sights and to immerse ourselves in something real and tangible. Birdwatching provides an excuse to get out into the countryside and to engage with the natural world, just as walking, riding or volunteering can. It is about extending our horizons, being expansive and engaging with the natural world around us.

Tufted duck gather for the winter

Good numbers of Tufted Ducks are gathered on the flooded gravel pits near home. Scattered among the more abundant Coot they prefer the quieter corners, away from the fishermen and their Sunday afternoon radios, tuned to the football. They are our most abundant and widespread diving duck, quite capable of sustaining dives down to 14m in search of food, something that gives them access to waterbodies unsuited to dabbling duck like Mallard and Shoveler. Tutfed Ducks are, therefore, a familiar sight during the winter months on many of the county’s flooded gravel workings.

Some of these Tufted Ducks are likely to be the same individuals that were here during the summer, perhaps even the individuals that managed to raise a family on the site. Many others, however, will have come from elsewhere. Birds from Fennoscandia and Russia may have arrived here as early as July, initially favouring much larger waterbodies (like Abberton Reservoir) where the birds gather to moult. Because Tufted Ducks breed so late in the year, with eggs often hatching during July or even August, many of the birds gathering to moult will have been males, the females remaining elsewhere to tend to the needs of their growing chicks. Smaller numbers of females may have arrived in August. Most of these birds remain here for the winter, dispersing from the favoured large reservoirs to smaller waterbodies, like the pits just south of Thetford. They will only move on if the waterbodies freeze over, halting access to the molluscs and invertebrates that they favour.

The numbers wintering here are dwarfed by the vast numbers that winter around the Baltic or on the Ijsselmeer in the Netherlands. Some winter further south, reaching the Black Sea and the Mediterranean. Although our breeding population has undergone a period of substantial growth, no doubt helped by the increasing number of gravel workings being flooded, wintering numbers have been fairly stable. This might underline the contribution of winter immigrants from elsewhere. One interesting aspect of the winter flocks is the dominance of male Tufted Ducks. On average, the males outnumber the females by 1.4 : 1, a reflection of the late breeding season and the early movements of the males. The males are instantly recognisable, with their black bodies and white flanks. Females are less striking, with dark brown bodies and paler brown flanks. A flock of ‘Tufties’ is always worth a scan with your binoculars, as it can sometimes hide one of our less common diving ducks; perhaps a Scaup or even a Lesser Scaup. I do like to see the Tufties on our local pits, since they seem more in keeping with the image of a wild duck than the usual Mallards.

Hail the Woodcock pilot!

For two weekends on the trot I have been on the coast at first light to watch the arrival of migrating birds, picking out my first Bramblings and Fieldfares of the winter from many other newly arrived individuals. A persistent theme of both weekends has been the numbers of Goldcrests, arriving exhausted from their recent sea crossing and keen to feed up on small invertebrates gleaned from trees and shrubs.

Goldcrest, by Mike Toms

I am in awe of these tiny creatures. Weighing no more than 7g, they are one of the lightest birds to undertake regular sea crossings when on migration. This feat can be considered all the more remarkable by the fact that they carry little in the way of fat reserves and, with little fuel with which to make the journey, it is little wonder that they arrive exhausted. Equally remarkable, to my mind at least, is that these diminutive birds are able to survive long winter nights and low temperatures by burning up energy reserves that may see them lose a fifth of their body weight over a single night.

Our Goldcrests, those that I encounter in the forest throughout the summer months, are largely sedentary in habits. With the possible exception of those from more northerly parts of Britain, these individuals spend the winter here, with some moving into gardens to take advantage of the fat products that many householders now provide. Those from elsewhere in northern Europe, notably northern Scandinavia and Russia, move south or southwest in autumn and it is these birds that have been arriving along the Norfolk coast over the last few weeks.

Many are young birds, perhaps reflecting a good breeding season, but maybe also underlining their short lifespan and the high degree of turnover of individuals within the Goldcrest population. We handled a good number at one of our coastal ringing sites the other day and it was clear that some had just arrived, being of low weight and low fat score (we can score the amount of fat on a bird because the fat is carried in a pit on the chest and along the belly), while others had been in for a couple of days and had already fattened up.

The arrival of Goldcrests is now just about over, as is the case for many of our other winter visitors and passage migrants. The arrival of Goldcrests is often linked to the arrival of Woodcock and Short-eared Owls, something that might explain the folk name of ‘Woodcock pilot’ given to the Goldcrest. Among wildfowlers it is sometimes said that the Goldcrest hitches a ride in the plumage of migrating Woodcock, but it is similarity in the timing of their autumn movements that really underpins the association.

On the move

Early autumn fogs hold the prospect of vagrants from the east. Small migrant birds, setting off from Scandinavia under clear skies, may find themselves drifted west across the North Sea. Here they may encounter a bank of fog or rain, which forces them down on to the East Anglia coast. If the combination and timing of these meteorological conditions happens in a certain way then many hundreds or even thousands of birds may seek the relative security of England’s east coast. This is a truly exciting event for the birdwatcher and an early morning walk among the dunes at Winterton or along the long shingle ridge towards Blakeney Point may yield some stunning birds. The sight of hundreds of Robins or Pied Flycatchers is one not readily forgotten. In with these more familiar migrants may be less commonly encountered species, including various warblers, thrushes and other delights.

Frustration comes when the forecast shows real promise and you have a full day of work ahead, with no prospect of an early morning dash to the coast. The walk out to Blakeney, which is to be recommended, is at least a half-day affair and not something you can squeeze in before work. It is a strange place, an exposed and empty landscape, touched by the hand of past human activities to leave a desolate air. In the clearing mists of early morning, ridges of shingle take on weird shapes and the landscape appears all the more alien. I sometimes feel as if everything else has gone, that human society has disappeared and all that is left are vague echoes of our presence in the form of discards from passing ships and former inhabitants of the point.

The Point at Blakeney has held some nice birds over the last two weeks, with one of my favourites – the Wryneck – reported by visiting birdwatchers. There are some birds that seem ideally suited to a particular place or landscape and the Point is the place that I most strongly associate with the Wryneck. This diminutive member of the woodpecker family was once a regular breeder across much of England but now it is effectively extinct as a breeding species – a real loss.

The arrival of these autumn migrants feels somewhat early this year, no doubt a reflection of the cold autumnal spell felt in the last two weeks of August. I usually associate late September and early October with visits to the coast to watch visible migration in action (the sight of pipits and thrushes passing south at dawn) or to seek out some of our rarer visitors. Even now, the long walk on shingle might be hard work but the rewards are likely to be worth it.

The Great Arrival

More than one author has conjured up the image of a Great Arrival, the 16 million or so migrant birds all heading north to summer on these northern breeding grounds. Most recently, in his excellent book Say Goodbye to the Cuckoo, Michael McCarthy speculated on how we would react were all these birds to arrive in a single flock. Such a flock would fill the sky; people would stop what they were doing in order to take in the spectacle and it would become an important signal that spring had reached our shores, celebrated with street parties and a public holiday.

Of course, our summer migrants do not arrive all at once in some grand flock; instead they turn up in small numbers or individually, with many arriving at night when the energetics of migration are better balanced. These overnight arrivals do provide one thing however; they deliver a sense of the unexpected to us birdwatchers, the thrill that the night just gone might have delivered some exciting find to an early morning trip to a patch of coastal scrub or waterside reedbed. Even those who would not describe themselves as a birdwatcher derive a thrill from seeing the summer’s first Swallow or hearing May’s first Cuckoo.

While these individual encounters act in some small way as a talisman for a wider arrival, the movement of this mass of birds, streaming out of Africa and up across Europe, goes largely unnoticed. Taken for granted, we find ourselves unaware of the problems faced by these many and varied travellers, problems which have resulted in dramatic population decline for some species. We only know of the changing fortunes of our summer visitors because of the work of organisations like the British Trust for Ornithology (BTO), whose partnership between researchers and birdwatchers provides regular monitoring of the birds breeding across Britain and Ireland. Yet even with this information we only know that something is wrong, we don’t fully know why. Are the numbers of Wheatears, Cuckoos, Turtle Doves and flycatchers falling because of difficulties here or is it because of problems on their wintering grounds or along their migration routes?

Recently, the BTO and RSPB have launched projects in Africa to look at our migrants on their wintering grounds, seeking to understand what is happening to the habitats they use during our winter. This work is only the start of a wider process which, ultimately, will need to feed into conservation action targeted at the different species across their whole range. The scale of this work also serves to bring home the message that while we view these birds as being ‘ours’, they are only ours for part of the year.

The first geese

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

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

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

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

On the move

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

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

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

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

Buzzards drift by

Last weekend saw an influx of Honey Buzzards into the county. These rather unusual birds of prey are very rare breeders within Britain but larger numbers may sometimes pass through on their autumn migration. Although the numbers reported over the weekend suggest a sizeable arrival, no doubt driven by prevailing easterly winds pushing the birds west of their normal migration route, it is unlikely to match the influx seen in 2000, when between 500 and 1,500 birds were thought to have drifted over. The Honey Buzzard is a long distance migrant, breeding predominantly in Russia, eastern Scandinavia, Germany and France (with fewer than 100 pairs breeding in Britain). Arriving here from late April, the birds face a short breeding season before setting off south again to the wintering grounds in the tropical woodlands that lay to the south of the Sahara. Unusually for a bird of prey, the staple food items are the larval stages of wasps and bees, obtained as the birds break open the nests of these social insects.

Adult Honey Buzzards depart from the breeding grounds some two weeks earlier than the young and migrating individuals are normally seen singly; that is, unless you happen to be watching at one of the main points where birds gather to make a crossing of the Mediterranean. At Gibraltar, many hundreds may be seen together, utilising thermals to gain the height needed to make their gliding flight over the sea.

Picking out and identifying migrating Honey Buzzards is not straightforward. Similar in size to the more familiar Buzzard (itself now fairly well established within the county), the Honey Buzzard shows a great deal of variation in its plumage. As such, you have to place greater emphasis on the structural characteristics of the bird rather than expecting to see clearly-patterned underparts. The wings of a Honey Buzzard are proportionally longer and narrower than seen in Buzzard and are held horizontally, or even slightly dipped, when in gliding flight. Watch a gliding Buzzard and you will see that it invariably holds its wings in a shallow ‘V’. Another useful feature is the head which, in Honey Buzzard, appears small in relation to the size of bird. I have heard the head referred to as being rather ‘cuckoo-like’ and this is a pretty fair description of both its size and the way it protrudes so prominently. Young Honey Buzzards show a greater degree of variation in their plumage than adults. Dick Forsman, a leading expert on raptors, reckons that juvenile Honey Buzzards are probably the most often misidentified birds of prey in Europe. As such, you can see why you need to be pretty sure of what you have seen before calling one in.

Catching up with the migrants

It was an early start, leaving well before dawn in order to be in place as the sun came up. Travelling up the A11 towards Norwich and passing through a series of heavy showers made the early start seem all the more ridiculous but as we approached the east coast our mood brightened, mirroring the clearing skies. By the time we reached the dunes at Winterton the weather conditions were just about perfect for picking up on the visible migration likely to be taking place, as small birds passed south on their autumn journey.

Watching visible migration can be an unpredictable pastime; earlier in the week there had been big ‘falls’ of birds much further north and we were uncertain as to our chances of catching up with good numbers of birds this far south. However, things can change and the weather conditions over western Europe were such that there should have been some good birds on the move. This unpredictability can both add to the excitement of this form of birdwatching (who knows what might turn up) and prove frustrating (with few birds passing over). It also involves a lot of standing in one spot and scanning the sky, scanning to pick out the small specks passing over and straining to hear a diagnostic call.

It did turn out to be a quiet morning, with only small numbers of birds passing overhead; a few finches, the odd wagtail and a single Tree Pipit. There were also a few Rooks, arriving singly from the east. Since we could not see the shore from our position it was not clear if these were migrant birds, arriving from the Continent, or local birds that had been feeding along the tide line. Then there was the Sparrowhawk, working its way along the dunes. Again, this could have been a passage bird, newly arrived, or it could have been a local, like us hoping to connect with some migrants. After an hour or so of watching it became clear that we should turn our attention to the bushes and shrubs that lined the back of the dune system. Here, sheltered, below the low cliff-top gardens were feeding and roosting opportunities for migrants that may have arrived the previous night. Working our way slowly south, we soon turned up a rewarding mix of birds, many of which were migrants. As well as Willow Wabler and Chiffchaff, there were Blackcap, Whitethroat and even Siskin. Spotted Flycatcher and Pied Flycatcher could be seen in the same field of view through the telescope and, in such good light, we were rewarded with a fantastic morning of birdwatching. We’ll be back again over the coming weeks to see what else we can pick up.

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?

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!

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.

20 pence flight from Norway

There is something special about birdwatching on the east coast during autumn. You get a real sense that vast numbers of birds are on the move, streaming into the country from across the North Sea. This was something that was brought home to me the other day as I walked the lanes around Happisburgh, enjoying the bright, clear weather that carries just enough edge to let you know that summer is truly over. Small groups of blackbirds were passing overhead, together with smaller numbers of redwings and occasional fieldfares. From the hedgerows, more ragged here than elsewhere in the county, came the high-pitched contact calls of diminutive goldcrests, busy searching for insects. Even though goldcrests breed in Britain (there are some 600,000 pairs nationally), these particular individuals were more likely to be migrants, freshly arrived from Scandinavia or western Russia.

As well as being the smallest British bird, the goldcrest has the distinction of being one of the lightest birds anywhere in the world to make regular sea crossings as part of an annual migration. For a bird that weighs roughly the same as a twenty pence piece (about 5.3 grams) such movements are truly remarkable. In some years, bushes and hedgerows at east coast sites may be literally ‘dripping’ with exhausted goldcrests during autumn. These are birds that must operate very close to their physiological limits. Information generated from bird ringing schemes, operating across Europe, has revealed that goldcrests breeding in the northernmost boreal forests are almost completely migratory in their behaviour. Birds from breeding populations situated further south are more likely to remain where they are to overwinter. Some coastal populations on the edge of the Arctic Circle in Norway also remain close to their breeding grounds in winter. By doing so, they have to cope with severe cold and nights that are 18 hours long. It has been calculated that these birds may burn off a fifth of their body weight each night, just to maintain their body temperature at a safe operating level!

This autumn has seen very large numbers of these tiny birds arriving on our shores. Even though the main arrival took place in the second half of October, and was centred on the Yorkshire and Lincolnshire coast, there still appear to be good numbers within East Anglia. Most mornings, while exercising my overly energetic spaniels in Thetford Forest, I encounter goldcrests foraging among the conifers. As if to reinforce the origins of some of these birds, I received a report last week of one individual caught within a mile or so of Thetford which sported a Norwegian ring. One wonders where the individuals I had seen at Happisburgh were from.