Most people are pretty familiar with the idea of migration. Animals make epic journeys that can cross countries and even continents. Many of these are seasonal, driven by changes in weather, temperature and the amount of daylight. All sorts of animals migrate, from hoverflies to whales, but it's birds that really bring migration to life. Through them, we can see migration in action, visibly unfolding in the air above us.

Various birds are on the move throughout the year, but spring and autumn bring the biggest changing of the guard. In autumn, our summer visitors are leaving, heading south in search of a warmer climate. They’re replaced by winter wanderers, fleeing the harsher weather of northern and eastern Europe.

Migration in action

Autumn is a great time to look for birds on the move. Migrating birds regularly follow features in the landscape, allowing you to stand and stare in awe as flocks fly above your head. Coastlines often produce spectacular movements as birds don’t want to fly above the sea, so they funnel along the edge of the land. But birds can also follow rivers, pass through valleys, or along the borders between different habitats.

The art of watching and recording these movements is known as visible migration, or ‘vismig’. With the right vantage point and weather conditions, vismig can be enjoyed just about anywhere – including in the heart of towns and cities! Get in touch with your local birdwatching group, or do a bit of research, and you can probably find a reliable site nearby.

October brings flurries of finches and thrushes, arriving from the continent. Ducks, geese and swans are also on the move. They migrate in noisy groups, constantly calling to each other to make sure they stay in formation. These calls are often what give them away. Listen out for the ‘ink ink’ of pink-footed geese or the trumpeting of whooper swans, drawing attention to the birds flying high overhead in v-shaped flocks.  

If you aren’t able to find a vantage point to enjoy migration in action, you can see the results gradually unfolding in the landscape around you. Lakes and reservoirs start to fill with wigeons and teals. Bramblings begin to appear amongst the chaffinches in woodlands. Redwings and fieldfares join the local blackbirds stripping berries from bushes. Each day could bring something new.

Wayward wonders

Seeing migration in action is always a thrill, but some birdwatchers have rarer tastes. They set out to find birds that have no business being anywhere near the British Isles. They’re known as ‘rares’ or vagrants. These wanderers are often rated on a scale from ‘scarce’ birds, which can be expected in modest numbers most years, to the much-anticipated ‘megas’ – birds that may have only been recorded here a handful of times.

Vagrants are basically birds that turn up out of their usual range. Something went awry during their migration, causing them to accidentally find themselves in the UK. It could be an effect of the weather, such as strong winds blowing them off course. Or it could be an issue with the bird’s own internal compass – or a combination of both. In autumn, strong easterly winds often bring unusual visitors from Scandinavia and Siberia. Meanwhile, storms crossing the Atlantic can carry vagrants all the way from North America.

One of the more common autumn vagrants is the yellow-browed warbler. They nest in the taiga forests of Siberia and generally spend the winter in southeast Asia. You don’t need to look at a map to realise that shouldn’t bring them anywhere near the UK! Yet each autumn, hundreds can be recorded across the British Isles, particularly on the east coast. They’ve become so common that some people think they might be establishing a new migration route, spending the winter somewhere in Africa.

There’s always a chance of something spectacularly rare appearing in autumn. It’s that slim chance that gets many birdwatchers out of bed well before dawn, scouring bushes and hoping for a ‘mega’.