So-called “summer migrants” are species which spend October to March (although dates vary) in warmer climes such as Portugal, Senegal, and the Congo.

This is because, in the UK winter, there are very few insects on which they feed.

The insects are the reason that they come in the first place!

There is such a super abundance in the summer that the birds have enough to not only be able to feed themselves, but raise a young family successfully too.

In the autumn, when it’s too cold for many insects to fly, the birds return south where the weather is warmer and there are flies all year round.

Believe it or not, though, some birds come here in winter for our milder weather.

The National Wales: Barnacle geese migrate to Europe to enjoy the milder wintersBarnacle geese migrate to Europe to enjoy the milder winters

Species such as barnacle geese breed in the Arctic when there are full days of sunlight and plenty of grass to feed on, and then, when the cold weather sets in, they migrate to Europe to enjoy the milder winters.

Some species have incredible migrations, such as the Arctic tern - which doesn’t just migrate north to south and back again, but does so across the entire globe, a distance of 22,000km.

The oldest known Arctic tern survived for 31 years, which means it travelled around 680,000km, which is the distance to the moon and back.

This species of tern breeds in the very north of Eurasia and then migrates all the way to the Antarctic Ocean, where it spends the “winter”, which of course there is summer again.

The Arctic tern has the longest migration of any bird, but it doesn’t have the strangest.

The National Wales: The Arctic tern migrates across the whole globeThe Arctic tern migrates across the whole globe

Lots of species follow a section of the Arctic tern’s journey and fly north and south, but not the red-necked phalarope.

A bird which weighs 27-48g, which is between one and two small bags of crisps, flies from Scotland to Peru and back each year. I know I couldn’t get that far on two bags of crisps.

Studies have shown that a bird which bred on the Shetland Isles, flew west and crossed the Atlantic Ocean before stopping over on the USA/Canada border.

It then flew down the east coast of the USA and crossed over onto the Pacific side of Mexico.

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From there it continued south until it reached the coast of Peru, where it stayed from October to April.

Although the peregrine falcon is known to be able to reach the fastest speed of any animal during one of its steep dives, also known as stoops, reaching 200mph.

It doesn’t fly at that speed in level flight. A more average speed of flight is 40-60mph. This is still enough to keep up with a car on an A-road.

Now imagine a bird which could keep that up for 4,200 miles.

That is what a great snipe has achieved.

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This brown and yellow wading bird looks very unassuming as it feeds at the edges of lakes and in soft mud, but when it migrates it can fly non-stop for 4,200 miles at 60mph.

It does this so it can travel from Sweden, where it breeds, to sub-Saharan Africa, where it spends “winter”.

How do they manage that? Well one of the fascinating aspects to bird migration is the height at which they migrate.

Cooler air is thinner and so requires less effort to fly through.

The coolness also prevents birds from overheating whilst using their muscles so much.

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This means that birds have been recorded flying at nearly the same height as Mount Everest (8,700m) - possibly the highest known flight of any migrating bird.

Smaller birds also use cooler air to travel through, although these birds fly at night. The air is cooler without having to fly as high, as such these birds are called nocturnal migrants.

Navigation over long distances can be hard enough as it is, but if you now add in that some species are flying at night or above the cloud layer then you can see that a range of techniques are required.

Day and low-flying birds tend to use physical landmarks, such as major rivers, roads, or mountain ranges, as it keeps them following a continuous path.

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High-flying species use the position of the sun, and species flying at night navigate by the stars.

Many of them use a combination of these, and even a few others that we are yet to fully understand.

Bird migration is so complex and fascinating, and we are understanding more about it all the time.

So next time you see a bird or group of birds flying reasonably high in spring or autumn, you might wonder which country are they going to next and what it is like there.

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