If you’re fortunate to share your daily life with swallows, as many of us are, you mightn’t necessarily realise just now reassuring a presence they are. They bring constant movement to the air, constant twittering to the sky. They’re a familiar but subtle backdrop to the summer months. And then, just like that, they’re gone. And everything just feels a bit….empty.
We’re not quite at that point yet, but with day length shortening, it’s not far off.
Swallows and martins
Just so we’re clear which bird we’re talking about here, swallows are the lightning-fast ones whizzing about the place with long tails, making impressively tight turns, swooping low over fields, all the while chattering and clicking to one another. That doesn’t necessarily narrow it down though, as that could also describe house martins.
Both swallows and house martins have blueish-black uppersides, and white undersides, but the martins also have an obvious white patch on their backs just above the tail.
When swallows settle, however, the differences between the two are obvious. I’ve been fortunate to have a few swallows land right outside my kitchen window from time to time, and that’s when you can really appreciate just what beautiful wee things they are.
A swallow’s head is a dazzling iridescent blue, with a striking red throat and face that the martins lack.
Swallows are larger too. They’re between 17 and 19cm long, with a surprisingly wide wingspan measuring around 30cm. House martins are small, around 12cm long, with a wingspan around 25cm.
In flight, the tails of martins are short, narrow and gently forked at the end, whereas those of swallows are long and deeply forked, due to the long streamers on either side of the tail. The length of these streamers can vary depending on the bird’s age and gender, but when swallows spread their tails out in flight, they have an attractive line of white dots across the tail feathers.
In the air, both swallows and martins are extremely manoeuvrable, which is essential for catching insects on the wing. I was once given a lovely personal display of this in my living room when a swallow flew through the open window, whizzed around the ceiling light-shade times without hitting anything, and then flew out again without so much as a word.
Answer me these questions three
By this point, for many people of a certain age, all this talk of swallows doubtless evokes memories of that wonderfully absurd scene from Monty Python and the Holy Grail. Fans will recall the crazy question that a medieval bridgekeeper poses to Arthur, King of the Britons, in exchange for passage across his bridge.
The bridge spans a misty abyss, its depths apparently endless, and everyone who crosses must correctly answer three questions. If they get a question wrong, an unseen force catapults them off the bridge, into oblivion.
Arthur steps up. The first two questions ask his name and his favourite colour, and are easily answered. The third is more random:
“What is the airspeed velocity of an unladen swallow?”, asks the bridgekeeper.
Before he answers, Arthur seeks clarification about what species of swallow the bridgekeeper is referring to.
“What do you mean? An African or European swallow?”
Caught off guard, the bridgekeeper admits he doesn’t know the difference and is immediately catapulted off the bridge by his own ignorance.
So…..what IS the difference between an African and a European swallow? Do such things even exist?
Well, swallows belong to a family of birds called Hirundinidae, which derives from Hirundo, the Latin word for swallow. And, just to confuse matters, the Hirundinidae family includes the martins. Arguments abound about subspecies, so you’ll see folk citing between 74 and 90 species in that global family, but it contains around 15 species of swallow (in the Hirundo genus) worldwide.
In the UK we have just one species of swallow (Hirundo rustica), so it’s not surprising we just call it the ‘swallow’. But in the parts of the world where several species of swallow co-exist, our swallow is distinguished as the ‘barn swallow’, due to its ready use of human structures. It can’t be termed an exclusively European species as it is enormously wide-ranging, being found from Australia to America, and there have even been sightings in Antarctica.
There are indeed some swallow species that live their lives exclusively in Africa, so yes, I suppose there are ‘African’ swallows, but it’s also entirely possible that the two choices presented by the bridgekeeper were the same species. You could, however, forgive medieval bridgekeepers and kings for being ignorant of this possibility, because it wasn’t until a swallow, ringed in Staffordshire in 1911, turned up in South Africa in 1912 that the world finally confirmed the staggering truth – that UK swallows fly to South Africa and back every year.
That fact still seems incredible to me, but it’s ultimately far more persuasive an explanation for the winter absence of swallows than some of the previous theories, such as hibernating at the bottom of ponds, or flying to the moon. Seriously!
Return ticket, please!
Our swallows will soon be starting this mammoth journey to Africa, and the reason they do so is threefold: food, weather and light.
The northern summer is (or at least has been) extremely productive for insects – its long hours of daylight mean hunting can take place for the bulk of the 24hrs and, given the average swallow brood will require hundreds, if not thousands of insects per day, it’s well worth spending summer here. But as we slide into autumn, none of those things can be relied upon, and the swallows must depart in search of the southern summer.
Barn swallow migration takes place across the entire northern hemisphere, with different regional populations taking different routes to different destinations: the North American population heads to South America; swallows in China head to either East Africa or Southeast Asia; and the destination for most of our swallows in Scotland is southern Africa.
That route takes them through England, across the Channel, down through France and Spain, across the Straits of Gibraltar to Morrocco, from where they either follow the west African coast or they cross the Sahara Desert.
There are numerous final destinations in South Africa where our swallows congregate, but one in particular, at Mount Moreland near Durban, is reputed to host around 3 million of them. 1% of the global population.
It’s a flight of more than 6000 miles, at an average speed of 20mph and covering as much as 200 miles per day. One swallow, which was ringed at one such roost in South Africa, was recorded in Whitley Bay in Northeast England just 27 days later! Quite astonishing really, for a bird that weighs little more than two £1 coins! That lucky swallow clearly had the wind at its back.
All kinds of unfortunate things can and do happen on migration. Swallows must face harsh weather and headwinds, predation from other wildlife, collision with vehicles, human hunters and, in a time of dwindling or unreliable insect numbers, possible starvation. The Sahara crossing in particular is very challenging, but for the Mount Moreland birds, their final obstacle upon arriving is the nearby airport at Durban, just a couple of kilometres away from their communal roost.
Thankfully, such is the importance of that roost for the global population of barn swallows, that the airport installed dedicated radar to detect large flocks of swallows at dusk and dawn (when the birds briefly gather in huge numbers). This enables them to delay or divert planes accordingly, safeguarding the birds. It apparently cost $300,000 to install, but that’s surely a small price to pay, given the location’s importance to global biodiversity.
The return trip back to the UK begins from around February. The average arrival date for the first swallows on the south coast of England is 29th March, but that date is progressively later the farther north you go – mid to late April across most of Scotland.
The cues for migration are environmental and include weather, and abundance or absence of food, but because day length also plays a pivotal role, the arrival date in any given UK location tends to occur around the same time, year after year.
My own personal observations of the first swallow in the Lomond Hills over the last decade or so certainly illustrate this nicely:
- 2022: 3rd May
- 2021: 14th April
- 2020: 22nd April
- 2019: 21st April
- 2018: 20th April
- 2017: 17th April
- 2016: 19th April
- 2015: 16th April
- 2014: 13th April
- 2013: 24th April
It’s remarkably consistent, all within an 11-day window, save for a late arrival in 2022 on account of bad weather in southern Europe and persistent northeasterly winds over the UK that slowed swallows’ northerly progress.
Interestingly though, every year, tempted by our warming climate, a handful of swallows ditch migration altogether and attempt to overwinter in the UK. It’s a gamble that could pay off after a mild winter, as they’d get first pick of nesting sites in spring, feeding off any early insect explosions and potentially raising more broods than their migrating counterparts. Conversely, a cold winter or spring with no insects to eat could kill them off.
But when swallows return in the spring, there’s no time to waste, and they immediately start building or repairing nests.
No time to waste
Swallows generally return to the same colonies, and around half of returnees will occupy the same nest as the previous year. An old nest will certainly require some repairs, but ultimately it saves time compared with starting from scratch.
As their name suggests, barn swallows favour buildings. But before humans started making structures in which swallows could nest, the birds would have nested on ledges in caves and on cliffs, although probably not in the numbers we now experience.
Indeed, some studies assert that it was precisely the arrival of human architecture that catapulted the swallow into territorial expansion and hyper-abundance, even helping steer its evolutionary path.
Swallows still favour buildings with open access and dim interiors, out of reach of most predators, but they are now extremely tolerant of noisy human beings, nesting alongside us in surprisingly busy locations.
I remember a very conspicuous nest on an interpretative panel at Craigmead car park in the Lomond Hills. And at Polkemmet Country Park in West Lothian, where the public loos were open all day, we had swallows nesting just inside the toilet doors. The loos were always locked at night, so in the end the Council had to cut small holes above the doors for the swallows to gain access regardless.
Nests are built on high ledges and are made from mud pellets, which the swallows scoop from the ground in their beaks, and then mix with saliva, grass and feathers. It takes more than 1000 foraging trips to construct a mud nest, which then sets hard.
A swallow will lay between 4 and 5 eggs. They require two weeks incubation before they hatch, followed by about three weeks before they fledge.
In many cases the birds will raise a second, or even a third brood in more southern climes, but the longer they linger (especially in Scotland) the higher the risk to the chicks’ survival. Unlike other small birds, who perch and peck at ground or tree-dwelling insects, swallows feed on the wing (flies, moths, beetles), and this food source obviously becomes scarcer as summer passes to autumn.
I can remember fluffy chicks in one of the Polkemmet Toilets nests well into the 3rd week of September, which seemed late to me, given that many of the other local swallows had already departed on migration.
Swallows mate for life but this doesn’t amount to a huge commitment, given what hazardous journeys they make. Mortality is high, and so the average lifespan is just a few short years. In that time, the more fortunate birds are likely to complete two or three return journeys to South Africa, which is impressive in itself. But some individuals are surprisingly long-lived – The oldest ringed swallow was 11 years, 1 months and 11 days, and was recorded in 1936.
Buzz and frenzy
Of course, no swallow article can be written without mentioning the Greek philosopher, Aristotle, for it was he who wrote that immortal line:
‘one swallow does not make a summer’
Written more than 2000 years ago, the vagaries of summer weather were evidently just as frustrating in ancient Greece as they are now. It’s a nice nature-based saying that now gets applied to all manner of situations where a single piece of good news doesn’t’ necessarily indicate that more good news will follow. It urges caution when you see or hear that first swallow in spring, advising you not to let your optimism get the better of you. Because sometimes, summer is elusive.
But then, the inevitable question that follows from that is…..okay, so how many swallows DO make a summer?
Well, if the recent weather-related despondency on social media is anything to go by, the more accurate saying should be ‘all the swallows in Africa do not make a summer’!
That’s down to personal preference of course. Personally, I’m very much enjoying the lack of heat and the reduced fire risk this summer. But what’s good for me isn’t necessarily good for others, and possibly isn’t good for swallows.
There’s a lot of doom and gloom on social media, and more widely, about both insect and bird numbers this year. A lot of it is anecdotal and based on personal experience rather than hard data. Nevertheless, I have to agree that there are considerably fewer swallows in the Lomond Hills this summer than I’m accustomed to seeing. I don’t have data on the number of individuals or nests, rather it’s just the simple fact that the air above the garden is lacking any buzz or frenzy.
The Lomonds currently have that ‘end of term’ feel, more reminiscent of September than July, when some, but not all of the martins and swallows have departed, and the hills start to feel empty.
Thankfully, recording long term data on swallows (and most other bird species) is something the UK is good at, so we do have a long-term picture.
The UK population is large, estimated at more than 700,000. But while that might sound a lot, the British Trust for Ornithology (BTO) has recorded a 23% decline between 1995 and 2020, although this masks a notable increase in the population that occurred between 1995 and 2010. And while things have been on the slide for a while, the last couple of years have seen a slight uptick in population since the low point in 2020.
Certainly, for much of this spring and summer the UK weather won’t have helped swallows in their constant search for flying insects. It has often been wet and/or dull, but as is always the case with migratory species, it doesn’t necessarily matter if the weather in your part of Scotland has been okay this year and you feel you are doing okay for insects. Of equal importance is what’s happening along a bird’s migration route. What’s happening in southern England, Spain, or indeed in South Africa affects swallows just as keenly as what is happening right here.
There are so many unknowns, and so much can go wrong, that I can’t help thinking that if I was a swallow, I’d cancel my flight to South Africa and just check-in to a Scottish hotel for the winter! For the moment though, the swallows don’t have time to ponder their snowbird vacation. Instead, they’re busy either rearing their recently-fledged young, or already starting on a second brood during their short Scottish summer. But it won’t be long till they start gathering on wires and fences with that air of impatience.
I don’t whether that’s a thing they genuinely do before leaving, or whether they’re just more conspicuous at the end of summer due to their numbers being swelled by this year’s newborns. But it does feel to me as though they gather in large groups before they fly south for the winter. I like to imagine they’re excitedly socialising in the departure lounge, swapping news, stories and phone numbers before heading off. Perhaps to meet up again when they get to South Africa.
And so, just as the swallows themselves are responding to environmental cues that tell them autumn is coming, we in turn respond to theirs, and so follows that inescapable feeling of melancholy.
So enjoy the intrepid aviators while they’re here, because soon they will be gone, and the air around and above you will calm, and fall silent. But all being well, with the love and support of countless people along their long migration routes, they’ll be back next year. And the next. And the next.
Long may that continue.