What swallows can teach us about global warming

What swallows can teach us about global warming

with David Hines

What swallows can teach us about global warming
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David Hines © 29 December 2019

A month ago I saw one of the most spectacular sights of my life.

I was walking my dog down my home street, and a tiny swallow flew up to one of the top branches of a Norfolk Pine, the tallest tree in our street.

A few seconds later another swallow flew up and perched beside the first one.

Then after a few more seconds they both suddenly dived off the tree spiralling down on a gradual dive. Doing loops, curving left, curving right.

What amazed me was that throughout this display they were both in perfect synch, turning the same way at the same time. It was like aerobatics, but far faster and more complicated than any human pilot would dare.

I found the explanation on the internet

The first bird was a female. The male had been trying to impress her by finding an ideal nest site, and she was impressed, but she also wanted to put him through a flying test. So she zig-zagged all over the place, while he struggled to keep up.

And if that was the game, he was a brilliant success.

All this to find whether he was a good hunter. Because swallows are hunters and they need to catch hundreds of insects a day. This victim was a cicada

The second one looks like a fly, and shows the kind of aerobatics he had been showing to his mate, in live hunting.

Other antics

I found that swallows spend almost their entire day flying, long gliding flights. Typically doing 320 kilometres a day.

They even drink while they are flying

So they need to live where there’s running water or a pond.

They do banking turns like a fighter pilot

A major puzzle for me

This was this was the first time I had ever seen such a display.

In fact when I was a child I never saw a swallow at all… this was in the 1950s.

Research showed there were few if any swallows in NZ in the 19th century

A few isolated vagrants came starting in 1920s.

And they came from Australia, probably blown across the Tasman, when they were trying to migrate to Tasmania, from New South Wales.

These first visitors musty have had lonely lives, like Robinson Crusoe, with no mates and no chicks.

But in 1958

Their first breeding colony began near Kaitaia and from there they gradually sppead throughout New Zealand.

They are now regarded as indigenous birds, because they arrived and established themselves without human help. and are dong very well.

The largest number of birds per garden, as measured by birdwatchers, is in Auckland where every eighth city garden has a swallow, and every 5th rural garden.

They are a great example of migration, but also of evolution, since they don’t migrate any more.

House hunters

They have adapted to nesting in human homes as in other countries.

They like their nests to be sheltered from the sun, so they like to live in barns, or under the eaves of houses, or under bridges. New Zealand has only had those for the last 150 years, which is possibly why they never established here before.

I had a second confrontation

with swallows outside my own home.

I was coming home for a walk when I saw a swallow zooming around in the porch by our front door. I thought he must have been looking for a nesting site, so I walked up and tried not to disturb him…. but I could hardly avoid him.

When I was right at the door, this bird came zooming straight at my face. I was a bit scared … but I thought it must be bluff, because he would come out the worse if he actually hit me.

But he suddenly halted about two metres from me, hovering with his wings spread out…. Their wings are huge for their size. They are only 16 cm long, but their wingspan is about double that. In fact they look like a small eagle

The one on the right is an actual eagle. But six times the size…. his wingspan is 130 centimetres.

I got my camera out to take a photo of him.

And he flew away, but only five metres or so, to our power cable.

I’m pretty sure this is a welcome swallow’ notice his forked tail, and very long wings, folded, but almost the length of his body. Then he took off.

But immediately afterwards, he came at me from the opposite side.

And when I went inside the house, and upstairs to the balcony to see if he was still hanging round. And he zoomed me a third time.

And a week later I got a fourth confrontation… when I was going out our front door …. and there he was hovering right in front of me.

I guessed his nest must have been in our next door neighbors place, because they have a carport that is three-quarters enclosed, a perfect nesting site, and they said yes.

So that brave visitor was not after our house; they just wanted to make sure we stayed in it, and didn’t pay any visits next door.

There is a lesson on evolution in this.

We usually think of evolution as an extremely slow event, with teeny changes being selected to give some members an advantage in changes of climate. But there some times when species make a sudden change, because they suddenly move to a new niche that suits them, or suddenly escape from a niche that has become horrible for them. When I say sudden, it doesn’t change their bodies immediately, but it immediately starts selecting a set of features that they already had in small numbers.

The ones that made it across the Tasman may have been stronger fliers than the average needed to fly across Bass Strait.

Migrating birds are an unusual case, because they are adapted to two climates, and this means they are:

very adaptable, but also

a very vulnerable, because it only takes one of their habitats to be out of action and their breeding cycle is broken.

A change of environment is not necessarily a disaster. Our swallows have broken with their Australian origins…. but New Zealand seems just as good for them.

I personally would not want to be a swallow in Australia right now, with Eastern Australia faced with huge bush fires.

Their breeding pattern

Another part of their environmental needs is mud, gathered from a riverside or a pond.

This one is gathering a mouthful of mud, and will spit it out…

And 2000 spits later they have a nest. Both parents build the nest, which looks very distinctive.

I saw a nest like this a week later when Marion and I visited Northland,. We stopped at a riverside café in Whangarei, and I noticed swallows going into a porch at the back of the building, and there was a nest on a drain pipe, and two chicks off the nest, but still running back and forth along the drain pipe, waiting for their next meal.

It didn’t come right away, so the two chicks flew off themselves.

Mating dance

The next chapter in their family life is the mating dance I mentioned earlier. And they actually have sex while they are flying as well. Well the male does the flying.

With swallows, sex is consensual. If the female doesn’t want to mate, she justs lifts her tail like this one, and he has to do a bit more persuasion.

They usually lay four or five eggs, and have about three broods every summer.

Parent and four mouths to feed.

Parent flying in to feed three chicks.

Parent can’t even reach the top of the nest because the chicks are so eager.

The young are still fed after they are off the nest (another cicada).

And are demanding their meal even before the parent reaches them.

Wrap up swallow saga

So they are very skilful adapters, and very climate sensitive. They can even tell a one degree difference in climate, according to one article I read. And minus two degrees is they coldest they will tolerate.

But they are also now one of us, natives of New Zealand, living in Auckland, and sharing our streets and gardens. They have only been here for 61 years, but some of us have been here lesss than that.

The biggest lesson for us, I think

Is that like swallows, we are fantastic migrators, and like them we have covered most of the globe, learning new skills as we went. Migrating for millions of years.

And though we are in a mess, we have made bigger changes than this, and managed.

Our origins as a species were in Africa up to 6 milllon years ago. The blue lines are thought to mark major moves out of Africa, with Neanderthals taking a branch left into Europe. Denisovans taking a major swing right into Siberia, and others going round the shoreline of India, into New Guinea and Australia.

All of these moves involved huge climate issues. The sea had to be lower to allow us to cross the sea to Australia, and from Siberia to North America.

The Neanderthals had to adapt to cold, because it was an ice age after they reached Europe.

And there were migrations back to Africa as well. So we now have genes from all these branches.

And I have just four snapshots of our migration, illustrating the pain, and the shame, and the victories.

One of the haunting signs of our early split was this picture of footsteps of australopiithecus afarensis. These footsteps were made in volcanic ash, which by strange coincidences have been preserved till today.

WE don’t know why they were walking there. Were they trapped in volcanic ash, or escaping it, or looking for a more friendly environment without knowing where.

But we know that those volcanoes divided the continent of Africa and provided a niche where humans changed.

But I cannot avoid the comparison with White Island, where similar volcanic ash caused a disaster taking with it people from all over the world, but especially Australia. And how we cared and comforted, and asked how we can do better in the future.

And the bushfires, fuelled by climate change also caused huge suffering, and massive efforts to help. But with the chilling thought that there are going to more such disasters worldwide, till we get the climate under control, if we can.

These disasters were all selective. Some of our ancestors survived them; others didn’t. Humans might survive an intensified heatwave if they have air conditioning. Others might not be able to afford air conditioning and be wiped out.

When there are disasters, manmade or natural, there are refugees, and for some of them the harm is compounded by rejection in other countries.

In this case it is Hungary, and the refugees are from Africa and Syria.

And the anti-refugee exclusion is now spreading into parts of Europe and the united states. With voters in luckier countries saying: don’t share your disasters with us.

But – still in Hungary, millions have escaped through the barbed wire, with their lives and their families if not their possessions.

So we are well equipped to face global warming.

WE have taken all those kinds of escape.

We have tried all those kinds of innovation,

the bad ones but also good ones.

And now we will have to do it again. For some decades at least.

MEDITATION

A poem from Israel two and a half thousand years ago.

The psalmwriter is grieving over persecution from powerful opponents.

And Felix Mendelsson put it to music.

And the song ends with the despairing, last hope of a would-be refugee

O for the wings of a dove

far away, far away would I rove.

In the wilderness build me a nest

and remain there forever at rest.