BTO: September is a month of change in the world of birds, as species such as swallows move out

Tough times ahead:  will this young Swallow manage to complete its journey to South Africa in the next three months? Photo: BTO/Jill Pakenham
Tough times ahead: will this young Swallow manage to complete its journey to South Africa in the next three months? Photo: BTO/Jill Pakenham

Although some swallows are still working hard to raise a late brood of chicks, many are already on their travels, perhaps sweeping over the chalk cliffs of Dover, flying around vineyards in France or hugging the Mediterranean coast as they fly south to Gibraltar, writes Graham Appleton.

By November or December, adults and youngsters will have exchanged a Suffolk stable for the sun of South Africa, 6,000 miles and a continent and a half away.

We know a lot about the routes taken by swallows, as they pass through Europe and on towards Africa, because they travel by day and gather in roost sites over-night. This day-time travel is quite unusual for our song birds; other species, such as warblers and flycatchers, are on the move at night, typically spending their days resting and eating. When a ringed swallow dies, it is more likely to be found than other species and it is relatively easy to catch them when they gather together each evening. Bird ringers studying migration in other countries sometimes have the bonus of finding a bird already wearing a BTO ring. Each bird that is found either alive or dead is another dot on the migration map http://blx1.bto.org/ring/countyrec/resultsall/rec9920all.htm.

As those keeping track of our BTO Cuckoos will have realised (www.bto.org/cuckoos), many of our summer migrants take ages to move between their summer and winter homes, making full use of ‘service stations’ as they go. One of the key issues for declining migrants, such as the fast-disappearing spotted flycatcher, could well be a disappearance of suitable stop-over points. With the length of each leg of the journey limited by the amount of fat that birds can carry, in order to fuel their flights, then the closure of service stations must be a big issue. It’s not as if they can pack a spare can of fuel!

Swallows seem to be doing better than most of our summer migrants, across the UK as a whole, which may be linked to the fact that they can feed as they travel, topping up on insects as they go. Having said this, we have lost a lot of our swallows from East Anglia. At the time of the last atlas of breeding birds (1988-91) there were hot-spots for the species in Suffolk. When the new atlas is published in November, it will be clear that there are far fewer swallows in this area, presumably reflecting declining numbers of insects, which could be linked to agricultural intensification and a continued move away from mixed farming.

As we make the most of each sunny September day, let’s enjoy the last few swallows of the year and wish them well as they tackle a journey that should never fail to amaze us.