Why do Swallows Migrate?

by Russ on May 29, 2013

Barn Swallows have blue backs, red throats and two long tail feathers.At this time every year, we welcome back one of the most charismatic of our summer visitors here in the UK. In April and May, the happy cries of the Barn Swallow can be heard echoing out across our countryside. These tiny birds have travelled and enormous distance to return to our shores, facing many perils in the process including thirst, hunger and becoming somebody’s lunch! But why do swallows go through all the hassle, why not stay here year round?

Swallows can often be seen flying low over water trying to catch flying insects.Many species of birds migrate. The longest flight from take off to landing is currently believed to be undertaken by our very own bar-tailed godwit, travelling a staggering 6,800 miles in one go! From hummingbirds to swans, birds have an incredible ability to migrate vast distances seemingly through instinct and memory alone. We still don’t fully understand how this process works but numerous research project has shed some interesting light on the subject. It has been found that when migrating from Iceland to WWT Martin Mere, Whooper Swans use landmarks to remember when to turn, one of the biggest of which is the Isle of Man.

To undertake these incredible journeys, birds like the barn swallow need a huge amount of energy and a good strategy. During the warm summer months, migrating birds fill up on enough food to see them through their migration. Swallows are insectivorous and will often be seen on a warm summer day chasing flying insects round fields and meadows.

Telephone wires are used regularly by swallows to rest on during the day.The reason they do all this is because of our climate. In the winter months, Britain’s temperature drops, the trees lose their leaves and many insects hide away and begin hibernating. For the swallows, who eat small flying insects, this means that if they stayed here they may face death through starvation. Instead, they leave our shores and head south to Africa, where the temperature is more than sufficient for their prey. You may then ask why the swallows bother to come back? One theory is the number of predators. In the tropics where it is warmer, there is a highly biodiversity and therefore a high number of species that could hunt young swallows.

When you travel North, the biodiversity starts to decrease because the temperature cools. Therefore nesting in Britain means that swallow families face less of a threat from predation which increases the number of chicks each pair can raise. In this way, swallows must be one of the most dedicated of parents in the bird world, covering up to 200 miles in just one day to reach their nesting grounds!

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{ 22 comments… read them below or add one }

Francis M September 12, 2013 at 1:20 pm

I SEE THE SWALLOW, AS A BEUITFULL SMALL FAST BIRD ON THE WING I HAVE TAKEN A FEW PHOTOES OF THEM, THEY HAVE NESTED IN MY SHEED FOR THE LAST TWO YEARS ,THIS IS THE THIRD YEAR I HAVE I HAVE LIVED HEAR MYSELF. BUT FOR SOME REASON THEY HAVE NOT NESTED IN THE OUT HOUSE THIS YEAR ,MAYBE ITS BECAUSE I HAVE A PUPPY DOG NOW ,AND HE STAYS IN THERE AT NIGHT , WELL WHAT EVER THE REASON, I TREET THEM AS MY FRIENDS,

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RR Lynn May 3, 2014 at 11:27 am

Our swallows have had 3 sets of ‘babies’ this season.The last set had 3 babies and was very late – april .These have stayed behind and parents do not seem to be around. As it is now May (South Africa),winter is just around the corner and I am wondering if the birds will eventually leave. What do you think?

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Russ May 8, 2014 at 10:05 am

Hi Rob,

Thanks for writing in.
That’s interesting that the young are still around, are you based in South Africa? In which case I haven’t come across a case of Swallows breeding there before, normally there would over winter in Africa and spend most of October-March feeding and resting, before returning to their Northern breeding homes in April and May.

I would expect your swallows will start migrating soon, but keep an eye on them – would be interesting to hear what happens next.

Russ

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Angela September 3, 2014 at 10:33 am

This year we have had swallows nesting on top of an outside light on our caravan. I expect them to migrate soon. Should I leave the nest there for when they come back

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Russ September 3, 2014 at 11:42 am

Hi Angela,

The swallows will be preparing to leave and it’s very much up to you whether you leave the nest there. If the swallows use it again next year, which is possible, it will save them time and effort if they have the old one to go back to but if you’d rather remove it over winter they will build a new one.

Russ

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Glenn September 11, 2015 at 9:25 am

Hi we are in the Forest of Dean Gloucestershire and we have never seen so many Swallows in one area some landing in trees (to many to count) and on power lines in the morning currently large flocks flying near by

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Lyn September 14, 2015 at 9:09 am

its now a cold and wet September in Fife, Scotland. There are 5 young swallows being fed by 2 adults in our barn. The rest left 2weeks ago. I’m sure that if they emigrate they young won’t survive and if they stay they will all starve. Is there anything at all I can do ??

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Russ H October 8, 2015 at 11:21 am

Hi Lyn. The best thing to do in this case is let nature take it’s course. Everything has been slightly late this year and the warmer October means some swallows have attempted a final brood before leaving. They are risking it, but if successful they will have five extra young. If cold weather catches them, the parents will migrate and have (hopefully) learned their lesson.

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gardiner September 16, 2015 at 7:32 pm

Here in Brittany we are a dairy Country, so have lots of Swallows. Alas, the Common Agricultural Policy has abandoned Milk Quotas. That means smaller and less efficient French Laitiers cannot survive – far less flies this year! But still our faithful friends have produced 2 broods this year.
One is a ‘late’ brood. By early Sept. , a pair of nestlings continue to roost at the nest site, while the parents and other siblings are not seen. Interesting sight , these. They ‘huddle’ together at night, unlike other fledglings. Hope they make back to somewhere warmer than here!

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Esther September 22, 2015 at 1:18 pm

Iam in Ireland deres swallows in my shed,dey will be migrating soon,is dere any way to find out where dey go to,an Izit possible for de same swallowed to return in my shade??

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Russ H October 8, 2015 at 11:19 am

Hi Esther, it is highly likely that the swallows that come to your shed next year are exactly the same swallows as last year. As for where they go, their precise location is difficult to establish. However, South Africa would be a safe bet.

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Esther September 22, 2015 at 1:19 pm

Where do swallows migrate to frm ireland

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Geoff Broome September 22, 2015 at 2:02 pm

I have been very lucky to have the lesser striped swallows return to the same nest for 15 years. I live in Elsburg in Germiston in South Africa. I am sure it is not the original pair, but there offspring. Cant wait to see them back again. Enjoy your birding.

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Anne November 6, 2015 at 3:47 pm

I’ve just seen what looks like huge flocks of swallow’s circling the skies above. I live in the south east of england directly on the coast and am curious to know if they would leave to migrate as late as November?

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Russ H November 6, 2015 at 3:54 pm

Hi Anne,

Due to the very mild October so far, birds have been slightly delayed in migrating South. The swallows you can see are probably hoping to catch a last few insects before leaving. It isn’t just swallows, bats are also still very active at night at the moment due to warmer weather.

Happy bird watching,

Russ

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Beryl High September 18, 2016 at 11:39 am

Hello There
We have a boatyard on the Southern Norfolk Broads and have been lucky enough to have swallows nesting in our large boat shed for many, many years.
We love to hear them arrive(the noise is deafening at times) and are always sorry to see them leave.(we forgive them for the mess they leave behind).
They have had 3 lots of babies this year and to date, have only had a couple of casualties when a couple of chicks fell from the rafters onto the hard floor.
We had one died on arrival, probably from exhaustion, which upset us all/
Our ‘family ‘ have just left us for warmer climes and we pray that they have a safe journey and return to give us lots of pleasure again next year.
They are sch fantastic birds.Good luck to them all wherever they are flying from.

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keith langley September 21, 2016 at 4:21 pm

Hi,

we get many swallows nesting each year in our stables and out house.
at least 3 broods each this year. the swallows migrated about 2 weeks ago now, all but one, it sits all alone in the out house. It does fly and seems to feed ok, maybe it was too week to undertake the journey. I don’t fancy its chances down here in cornwall over winter. can we help.

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Russ October 11, 2016 at 8:10 am

Hi Keith,
If the one hasn’t left yet it will hopefully be busy catching food for migration. This sometimes happens with one or two from the nest. The best thing to do is keep an eye on it. Not all young swallows from this year will find enough food to make their first migration, but being on the south coast your swallow has a much better chance as it stays warmer down there for longer.

Best of luck!

Russ

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Vicky Hudson October 4, 2016 at 6:43 am

What is the trigger for Swallows to migrate back to Africa, is it temperature or daylight or lack of insects?

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Russ October 11, 2016 at 8:06 am

Hi Vicky, it is most likely sunlight as this is a constant that doesn’t change and is a good way to work out when winter is coming. However, if we had an unseasonable cold snap or the insect population did drop early, this may force the swallows to migrate earlier (or later) than normal.

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Natasha Giroux February 5, 2017 at 5:16 pm

Dear Nature Talks and Walks,
As part of my research into how seasonality is changing in the UK I am trying to find information on why various bird species leave Africa and migrate to the UK. You suggest here that the general consensus is that swallows leave Africa due to higher numbers of birds of prey but you don’t reference this. I wondered if you could point me to any studies on this as I cannot find appropriate literature anywhere.
Your help would be greatly appreciated.
Yours sincerely,
Natasha Giroux

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Russ February 7, 2017 at 12:50 am

Hi Natasha,
Many thanks for getting in touch. The theory of why birds migrate being down to numbers of predators is one I learnt at university. As for a reference, you are best searching through google documents (or other search engines) for scientific papers that discuss this. I will see if I can find anything in the meantime.
Good luck with your research!
Russ

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