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Fly Away Home – bird migration in the city

March 6, 2012

This article is published in the spring 2012 edition of Lost In London magazine.

For Boris Island, read Flyway to Hell – London is a heavenly place for bird migration, and has served as a first-class avian international airport for millenia, writes Mark James Pearson

Of all the reasons to fall in love with London, there are two that transcend all others for me. Firstly, and perhaps most obviously, it has to be the city’s rich and enviable diversity; whether you’re a native or (like many of us) an adopted son or daughter, London fosters a fascination with the unfamiliar, where the exotic becomes integral.

One of many Common Whitethroats that travel thousands of miles every spring, just to raise a family in London

Secondly, it’s the capital’s inherently transient dynamic. To me, London’s true essence is ephemeral; like the river it clings to for dear life, its communities and populations ebb and flow, constantly rejuvenated and reshaped by new waves and changing tides.

But try thinking of those reasons not in relation to our own species, but to hundreds of others we share our city with. They apply just as potently to a genuinely epic, endlessly fascinating story which few of us are intimate with (or often even aware of), but which is playing out around us, throughout the spring and beyond, day and night here in London – bird migration.

Most of us know something of it on a wider scale, perhaps as transmissions from far-flung, exotic locations, delivered in high definition to our living rooms; some of us may have brushed against it directly, looking up to see disorderly skeins of geese following the coast, or pausing to watch a skyful of Swallows hawking expertly over a local lake.

Caspian Gull, Rainham landfill site, East London – one of the best places in the UK to see this rare East European visitor

Relatively few of us, however, are aware of its significance and extent on our doorsteps, and enjoying it first-hand is by no means a specialist exercise confined to a few exclusive places. On the contrary, anyone can connect with this traditionally secret world simply by taking an early morning walk in a local park at the right time of year, or even just looking up for long enough.

The movement of birds in, over, through and around the capital is a complex business, occuring throughout the year, and for a variety of reasons. In the height of summer, for example, young birds disperse from their natal areas, often in initially random directions; in the dead of winter, meanwhile, London recieves more than its fair share of refugees fleeing frozen conditions on the continent, seeking sanctuary and a comparatively mild climate.

But broadly speaking, avian migration is inextricably linked to spring and autumn. In the spring, it’s essentially a northbound movement, and in the autumn, essentially southbound. While most of us are busy struggling to make it through the seemingly endless depths of the late winter, this magical annual phenomenon has already begun in distant places around the world, and it’s only a matter of weeks before the vanguard reaches London.

A Red Kite glides low over central London rooftops, against the Houses of Parliament – an increasingly regular sight in urban areas after being on the brink of extinction in the UK just a few decades ago

For some of us, it’s the knowledge of their imminent arrival which keeps the wolves at bay during that most forsaken of times in our annual cycle. That thousands of miles away these epic journeys are underway is simultaneously comforting, exciting and awe-inspiring; that London is both a valuable pit-stop and a crucial final destination for so many of these intrepid, highly-skilled travellers is something to celebrate, cherish and protect.

The migratory species that frequent our city are a rich and varied clan, from tiny, insectivorous warblers to powerful, impressive birds of prey and everything inbetween. They utilise a broad spectrum of skills and aids to navigate successfully, many to the same place, year after year, generation after generation. Lack of space prevents more detail here, but one such skill is the use of traditional flight lines and visual aids.

Hence, an Osprey bound for a solitary loch in the Scottish Highlands and crossing London en route from its African wintering grounds may follow a flight-path deliberately plotted not only according to natural landscape features such as rivers and valleys, but to human-made features, such as buildings and roads. Hard to believe as it may be, the slide rule, Roman-built A10 out of Liverpool Street can be as important a navigational aid to such an impressive long-distance migrant as the relative positions of Taurus and Cassiopeia in the night sky.

Northern Wheatear – coming to a park near you, fresh out of Angola

Various habitats within the city are valuable refuges for migrants, be it for a few hours or for a whole summer. From a migratory bird’s perspective, expansive, truly urban areas are effectively deserts, unwelcoming and fraught with danger; but despite massive losses over the recent times, London is still blessed with a comparatively large variety and combined area of semi-wild spaces and green oases.

Flagship reserves (including the Wetland Centre and Rainham Marshes) justifiably spring to mind, but crucially London is also blessed with an archipelago of islands in the concrete ocean – from the heart of the city to its suburban fringes – that make it arguably one of the greenest major cities in the world, and a great place to enjoy and nurture birdlife.

To multitudes of tired, hungry migrants, the sanctuary of our parks, woodlands, wetlands, gardens, brownfield sites and other semi-natural habitats is absolutely critical, however modest or isolated they may seem. And any habitat which has escaped development, by accident or design, is of more value than ever in these dark days of short-termist, blinkered profiteering.

Black Redstart – a rare London breeding bird, found almost exclusively in urban wasteland and brownfield sites in the capital

To a Spotted Flycatcher, for example – a barely Robin-sized, long-distance migrant which travels thousands of miles to reach the UK every spring – the woodland glade habitat recreated by rows of adjoining back gardens can be both a temporary life-saver and a place to set up the family home. To a Whimbrel bound for the Scandinavian tundra, meanwhile, the bountiful mudflats of the Thames are as essential as the marshes of the Camargue.

While most of the Thames’ formerly expansive floodplains and marshes have long since disappeared under the bulldozer, what remains – a precious estuarine environment still teaming with multitudes of waders and wildfowl – is not only of unrivalled local importance, but is an essential piece of a uniquely valuable jigsaw, that includes various other sites on migration super-highways across the planet.

As a long-serving Hackneyite (having migrated from the Yorkshire coast long ago), my adopted city has provided me with innumerable avian highlights, usually involving the joys of migration, and most often in the spring. My advice – pick up a bird guide from you local library, get up early and don’t look back. And remember, London’s enviable capacity to accommodate, integrate and welcome myriad new arrivals is by no means reserved for noisy bipeds.

Species accounts:

(Common) Swift Apus apus

No other bird is so quintessentially London, supremely exotic and perfectly symbolic of the arrival of spring. Swifts reach us after a punishing journey from Africa towards the end of April, with most arriving in May. Screaming parties gunning low over our streets are an evocative feature of midsummer London, and are a sign that ‘our’ Swifts will soon be on their way again, after as little as three months in the city.

They’re best told by a combination of their unique profile – cigar-shaped bodies, scythe-shaped wings (earning them the colloquial name of ‘flying horseshoes’), and short, forked tails, and their flight behaviour – stiff-winged, acrobatic and often very social.

Unusually, Swifts rarely touch terra firma except to raise their young; a bird born in London this summer will, incredibly, most likely stay airborne for the next two years. Swifts feed, mate and even sleep on the wing, and – being almost exclusively reliant on crevices in our buildings for their family homes – make perfect neighbours; they’re wonderfully acrobatic, consume thousands of insects per day, and even pair for life.

Their population is crashing alarmingly, with factors including loss of existing nest sites due to development and ‘improvements’, and lack of available nest sites in new build. For more information, and ways you can help this iconic and magical species, go to http://www.londons-swifts.org.uk/

Willow Warbler Phylloscopus trochilus

Willow Warbler, London – via Africa

Willow Warblers are small, bright, insect-eating sprites that – despite weighing only about as much as a pound coin – migrate from their winter quarters in Africa every spring to reach our shores. They’re one of the commonest birds of the northern Eurasian forests, but due to a steady decline in the UK in recent years, are now amber-listed (of moderate conservation concern).

The first birds reach us at the very end of March, and most pass through during April and early May. They utilise a variety of habitats, and spring migrants can be found singing in woodland, parks and even gardens across London.

Very similar in appearance to the more numerous Common Chiffchaff Phylloscopus collybita – both are olive-green above and pale below, with a yellowish wash – they’re seperable visually with practice, but are much easier to identify by their distinctive, ‘cascading warble’ song (see below).

Willow Warblers undertake a complete moult twice a year, on both breeding and wintering grounds – making them apparently unique among all birds. No-one knows for sure exactly why this is, but most theories relate to the species’ extraordinarily long distance migration.

To learn more about Willow Warblers and other British migrants, go to the British Trust for Ornithology website (www.bto.org/about-birds); to listen to and learn their distinctive songs and calls, go to the wonderful (and free) http://www.xeno-canto.org/.

Common Tern Sterna hirundo

Common Terns are summertime Londoners with an epic inter-continental migration, and as a result are equally familiar with the Namibian coastline as they are with the Walthamstow skyline. Wonderfully graceful and bouyant in flight, they’re by far the commonest tern species in the London area, and are the only member of their family to breed within the capital.

A combination of their aerial grace and long tail-streamers earned them the appropriate alternative name of Sea-swallows, and their pale grey, black-capped plumage further them (The much rarer Arctic Tern Sterna paradisaea is similar in appearance but is a scarce bird in London and almost exclusively maritime).

Common Tern, Hackney (via the southern seas)

Feeding almost exclusively on small fish (caught by an impressive hover-and-dive technique), Common Terns breed in colonies close to water, and in London their continued presence is almost entirely due to the provision of artificial rafts on reservoirs. These small, gravel-covered islands make for ideal nesting sites, aggressively defended by breeding pairs.

Arriving (like so many of our summer visitors) in April and May, Common Terns can be found over almost any open water in the capital, including canals, rivers, large ponds and lakes in parks, on migration and on feeding forays from local colonies. For close-up, guaranteed views, however, make for one of the established colonies – Rye Meads RSPB reserve and Walthamstow Reservoirs are both recommended.

Mark James Pearson

All words and pictures – copyright Mark James Pearson 2012

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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