Millions of swallows have begun the dangerous journey thousands of miles north for the European summer. These birds have fascinated humans for centuries. What can their epic flight teach us?
What are swallows?
They are small songbirds with dark, glossy-blue backs and red throats. They have pointed tail streamers which give them a characteristic shape. No larger than a shoe box and only weighing 25 grams, they can fly at speeds of up to 35mph.
Swallows are insectivorous, snapping up food mid-flight. They never land to drink, either, sipping water from lakes and ponds on wing. There are thought to be around 15 million swallows in Europe, with the largest populations found in Bulgaria and Poland.
Where do they live?
Swallows are migratory birds, which means they spend different seasons in different continents – following the warmer weather. They spend their summers in Europe, arriving in April after a six-week journey from Africa and the Indian sub-continent. The northern summer months are spent bringing up broods of chicks.
The swallows return south in late September and October. The 6,000-mile journey cuts down through France, Spain and Morocco. British swallows then cross the Sahara before eventually landing in South Africa and Namibia. The journey is perilous. Many die from starvation, exhaustion and in storms.
How do they know when to go?
There are plenty of environmental triggers for the migration. These can be changes in food supply, daylight hours and temperature.
But all migratory birds also have cues built into their biology. As a reaction to the environmental changes, glands in the body release hormones into the system. These cause the birds to behave differently. They become restless and gather together in flocks and murmurations – and are known for collecting together in lines on telephone wires in the early autumn.
What about where to go?
Migrating birds appear to navigate using mental maps of the terrain, the position of the sun, moon and stars – and the earth’s magnetic field. This form of navigation is called magnetoreception and is common to many birds, even those who do not migrate.
How are they represented in culture?
Swallows have existed in human folklore for millennia. Ancient Greeks were fascinated with swallows. In mythology, gods could change into the birds. Grieving mothers thought the birds carried the souls of lost children. Killing a swallow was deemed to be unlucky. These superstitions lasted. In the UK, up until the 1960s, it was believed that killing a swallow would affect cows’ milk.
For most European cultures, the swallow represents the return of spring. Aristotle first wrote “one swallow does not make spring”. The birds have been the subject of writing ever since. Keats mentions them in his poem To Autumn. They make an appearance in Monty Python. And a Ukrainian new year song, The Little Swallow, has become one of the most famous carols on the planet after being played in Home Alone.
What can they tell us about climate change?
Swallow numbers have been declining since 1970. This is down to changing weather as a result of global warming. Droughts threaten the birds in their winter homes. Meanwhile, colder springs with late frosts in Europe make it harder to breed – and exceptionally hot, dry summers have led to high death rates.
Climate change could also be altering the whole pattern of migration. Last November, swallows were spotted in England two months after they were due to leave. Now, scientists at Yale warn that warmer weather is encouraging swallows to return too early. Just as swallows have always marked the seasons, they are now reminders of the human impact on the planet.
- Should birdwatching be compulsory in schools?
- Birds are a huge part of everyday language. How many phrases and expressions involving birds can you think of? Make a list, alone or as a class.
- Their diet consists of live insects that they catch mid-air.
- On wing
- An estimated 4,000 species of birds make seasonal journeys across continents. The longest journey is made by the Arctic Tern, which travels 90,000km from the North Pole to the South every year.
- Full of danger or risk.
- A large group of birds that all fly together and change direction together. The phenomenon is most common in starlings.
- Folklore suggested that killing the birds would result in bloody cow’s milk – or cause the milk to dry up altogether.
- One swallow does not make spring
- Now a common proverb meaning that one single positive event does not mean that everything that follows will also be good.
- Monty Python
- In Monty Python and the Holy Grail, King Arthur is forced to answer the following question to prevent his death: “What is the airspeed velocity of an unladen swallow?”.
- Home Alone
- The song was translated into English as “Carol of the Bells”, but its original lyrics tell the story of a swallow returning and announcing spring.
- Yale University is an Ivy League school in Connecticut, US.
- Too early
- Warmer weather earlier in the year cause swallows to return and begin nesting, only to be affected by late-season cold snaps.