Swallows – the sight of summer

With their cheerful, twittering song and impressive aerobatics, the sight of swallows soaring overhead is something many of us look to every year.

These impressive little birds fly all the way from Africa (an odyssey of over 6,000 miles) to enjoy the UK’s bounty of insects. Once settled, they set about finding a mate, and as soon as a partnership is established both the male and female start building their nest.

The nest is a cup-like structure built from mud and lined with grass and feathers, and is usually constructed under eaves of buildings. It is likely that swallows once nested in caves and on cliffs, but they now use man-made structures such as barns and the overhangs of decks and patios. A single pair can make up to 1,000 trips to collect mud for the nest, which may hold up to eight eggs.

Males will defend their nest fiercely, but even so, there may be rivals waiting in the wings. Males without a mate will often seek out the nests of other swallows and attempt to cuckold the established male of the nest by wooing the female. However, the majority of the time, a female will only accept a new male is if their current partner dies or if the nest fails. If a rival male finds an unattended nest with young chicks, he may kill the entire brood, ensuring the nest fails and making it more likely that the female will choose him over her established mate.

As swallows only feed on flying insects such as horseflies and bluebottles, their food source starts to dwindle when the weather cools in the autumn. At this point they head back to Africa, usually during September and October.

They cover approximately 200 miles a day, generally flying at a speed of around 20mph – the fastest known swallow was travelling at 35mph! The journey home is a hazardous one, and many swallows will succumb to starvation or exhaustion. As a result, populations fluctuate year on year.

However, there is plenty of time to see swallows before they leave, so keep an eye out for them this summer and enjoy their spectacular aerial displays.