What is arguably one of the most exciting times of the year – if you are a birdwatcher – is just around the corner: spring migration. The time when around 15 million birds make their way from various parts of southern Europe and Africa to take up summer territories, find a mate and raise a family here in the UK.

We are already seeing signs of birds on the move, albeit from 3,000 miles away. The British Trust for Ornithology's (BTO) satellite tagged cuckoos have left their winter quarters in the Congo rainforest and are heading to their first stopover in West Africa, where they will rest and feed-up before attempting the hazardous crossing of the formidable Sahara Desert and the flight back to the UK.

Two birds are already in West Africa, one in Sierra Leone and the other in Ivory Coast; they will stay there until around the end of March.

Whilst we can’t follow birds such as the swallow and the wheatear on their migration in the same way that we follow the cuckoos, we know that they will be well on their way to the UK. The swallow having left its winter quarters in South Africa around a month ago, and the wheatear in the last couple of weeks.

Traditionally, wheatear is the first long-distance migrant to arrive back in the UK each spring and there has been a report already of a female on Heacham Beach, Norfolk on 26 February. Any warm southerly airflow during the next week should see more of these wonderful little birds arriving here.

Why move?

But it is not just about birds coming here after spending the winter in Africa. Many birds make their way here for the winter, escaping harsh conditions further north.

Light southerly winds during the next few weeks will see birds like redwings, fieldfares, whooper and Bewick’s swans heading back north on their migration to their breeding grounds in Iceland, Scandinavia and northwest Russia.

You might ask why any of these birds move at all?

In the case of the birds that come here from the north the answer is fairly straightforward: if they remained far to the north, at some time during the winter they would be overcome by incredibly low freezing temperatures and deep snow cover.

Both of these conditions might not immediately prove fatal to the birds but would make it extremely difficult to find enough food to survive. So they are left with a choice, stay put and almost certainly perish, or move and hopefully survive.

For those birds that leave southern Europe and Africa to spend the summer here it might not seem so obvious why they do. The conditions in both of those places are reasonably good throughout the year and many species of birds do breed there, and this is probably the point – many other species of birds breed there, increasing competition for nesting space and resources.

By moving that little bit further north the competition for both can be reduced, and if you time it right you also hit the seasonal flush of invertebrate life that is very much a feature of a northern spring, helping you to raise that all important family and ensure the future survival of your genes. Of course there are many other factors too.

You can follow the BTO cuckoos on migration.

Paul Stancliffe is Media Manager for the British Trust for Ornithology.

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