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Taking flight.

In the coming weeks millions of birds will take part in an unseemly stampede as they jostle to flee the UK. Liam Creedon reports on the great autumn migration THE next time you find yourself standing outside with a few moments to kill, stop, and have a listen. The chances are that you won't actually hear that much in the way of birdsong.

August and early September represent the bird watching equivalent of being stuck in the doldrums.

By the time the tail end of summer rolls around many birds have raised several broods and run themselves into the ground.

Some will spend this time quietly trying to feed up for winter. Others will have already departed our shores for sunnier climes.

By the time you read this there is a good chance swifts will have vacated our skies and will be hundreds of miles away, heading south, fast.

Our cuckoos scarpered weeks ago but this year we were afforded a fascinating glimpse into the secrets of their migration. Tiny satellite trackers fitted by the British Trust for Ornithology (BTO) revealed where and how the cuckoos travelled - across the Sahara to their Central African wintering grounds.

In the coming weeks, telegraph wires will bulge with the added weight of thousands of swallows, gathering together before heading south.

We understand birds migrate principally for food security, but how they make these incredible journeys is still something of a mystery.

We know they are fantastically well adapted. Many can rapidly gain Fantastic Migrant cross the weight prior to departure which is stored as fat to provide energy en route.

Breast muscles used to power flight can temporarily swell, livers can increase the rate of fatty acid production and intestines can lengthen to improve food uptake.

But how they navigate is still widely unknown. Do they follow the Earth's magnetic field, do they have an in-built compass, do they learn routes from their parents or do they navigate using the position of the sun and stars? Paul Stancliffe, from the BTO, explains: "It is thought all migrants have an amount of biomagnetite in their brains which helps them navigate using magnetic north. Polarised light and visual clues are also used, the latter probably more important in a bird's second year of migration.

"Some birds have receptors in their eyes that enable them to see polarised light and even when it is completely overcast they can tell where they are in relation to the sun.

"Genetic cues are also used.

A juvenile cuckoo migrates to Africa in its first year having never seen another cuckoo."

So the coming weeks herald the most exciting time of the year for many birders. Certain coastal spots will resemble an avian Heathrow as birds leaving are joined by migrants coming in and others stopping to rest while on passage.

But what birders are really hoping for are storms that blow rarities off course.

journey: So, in the next few weeks, keep your eyes to the skies, you could be in for a treat. ? To find out more, visit www.bto.org

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Fantastic journey: Migrant cuckoos cross the Sahara Many migrant birds (main and inset) are busy feeding up to fly thousands of miles south as summer ends
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Publication:Daily Post (Liverpool, England)
Date:Aug 17, 2011
Words:541
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