Arriving one by one, the swallows that make summer - and signal a
By Michael McCarthy, Environment Correspondent
22 April 2003
One of the great wonders of the natural world is suddenly visible for
the first time – heralding a transformation in the understanding of
The miracle of bird migration, when millions of summer visitors pour
into Britain to nest from their winter quarters in Africa, can now be
watched as it happens. An unfolding picture of the return of each
species, from the swallow to the cuckoo, from the first trickle of
early individuals to the final tide weeks later, is being played out
before a worldwide audience on a remarkable website.
It has been made possible by harnessing the energy of birdwatchers all
over Britain to the power of the internet, and it is likely to throw
much new light on the whole phenomenon of bird migration.
Although people have always recorded the first returning swallow, the
first cuckoo, the first chiffchaff and the first of whatever their
favourite species may be, the general pattern of a spring's migration
across the country has never been visible before.
The project that makes it possible is called Migration Watch, run by
Britain's leading bird research organisation, the British Trust for
Ornithology (BTO). On the website – www.bto.org/migwatch – is a series
of animated maps of the British Isles, which update themselves on a
daily and weekly basis with the records of 1,300 birdwatchers across
the country looking out for incoming migrants and sending in their
sightings via the internet.
The maps mark sightings with red dots that represent grid squares; they
progressively fill up the map until the country is covered in red.
Watching it happen is almost like watching Britain catch chickenpox.
Take the swallow – one of the first indicators that warmer weather is
on the way. After two weeks of blank maps – the records run from
mid-February – the first lone red dot for 2003 appears in the week
beginning 2 March on the south coast. This was a single bird, recorded
at Shoreham airport, West Sussex, on 5 March.
The following week, from 9 to 15 March, there are four red dots as
birds are seen in West Sussex (Pulborough), Somerset, Northamptonshire
and Ayrshire in Scotland. The week after, from 16 to 22 March , there
are 14 red dots as birds start to turn up across the country; the week
after that there are 40 and the following week there are 45. Then the
tide suddenly starts to flood in. In the week from 6 to 12 April, there
are well over 200 sightings and last week, the maps show, swallows were
pouring in with nearly 500 observers reporting the birds.
One fact that is already clear is that the great mass of swallows are
arriving in Britain in 2003 a week later than they did last year, when
Migration Watch was started, probably because a cold snap in Spain and
Portugal in late March delayed the birds on their trip from Africa.
Such patterns are visible for the first time because the use of the web
makes the data immediately available.
Dawn Balmer, the Migration Watch organiser, said: "Only since people
started using the internet has it been possible to do something like
this. Because migrants come in every day, you want something that
provides really fast feedback. We can update the website every day
showing a really fast pattern of migration.
"Imagine doing that manually – it would be months and months before it
was all typed up. With lots of traditional surveys it's been months or
even longer before you get results but here it's the next day. And it
gives people a lot of pleasure to see their own dot on the map."
The maps illustrate the arrival of more than 50 migrant bird species. A
glance at them shows the first Migration Watch cuckoo of 2003 was heard
on the eastern outskirts of London at Darenth Lakes in Dartford, Kent,
on 24 March, followed during the next week by three more early birds in
Hertfordshire, Nottinghamshire and Gloucestershire.
There were only seven more in the succeeding fortnight, but then, last
week, the real influx of cuckoos into Britain began to get under way,
with more than 50 reports from observers: it will probably peak this
week or next. And just like the swallows, the cuckoos are a week later
than last year.
Another infallible marker of spring, the chiffchaff, has been here in
numbers for a month. The maps show the birds began flocking into
Britain in the middle two weeks of March. Its close relative the willow
warbler, which has a much greater distance to travel (it migrates to
southern Africa as opposed to west Africa in the chiffchaff's case) is
just turning up in large numbers to Britain now.
It has been estimated that some 16 million birds pour back into Britain
every spring from the warm south where they have spent the winter
(mainly Africa). These are thought to include something over a million
swallows; between 25,000 and 50,000 cuckoos; perhaps 1,300,000
chiffchaffs, and as many as 4,500,000 willow warblers, which, although
not nearly so well known to the public as other common garden birds,
rank as Britain's most numerous migrants.
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