STOEP CHAT

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16 March 2023

Terns and Storms

I’m sing on the balcony looking at a flock of terns that have landed on the beach at Noetzie.

“That means bad weather’s on the way,” my grandfather used to tell us as kids.

He was oen right.

We have a permanent flock of seagulls on the beach, but terns come to roost only occasionally, oen when there is a westerly blowing, and westerlies oen bring stormy weather

It intrigued us as children to think that these lile birds could tell that bad weather was on the way and seek refuge on the beach.

Since then I have learned that seabirds know quite a bit about approaching weather, and take acon to avoid the worst of it.

We have all seen television coverage of cyclones and heard the roaring wind and lashing rain. But here is something I did not know: cyclones also produce something called infrasound, a sound so low that humans cannot hear it.

Infrasound can be detected more than 1,000km away from the cyclone itself. Astonishing.

Some researchers think seabirds may be able to detect a cyclone’s infrasound long before the cyclone reaches them, and take acon to avoid it.

Makes a comical mental picture: a bird cocking its head on a sunny day, then tweeng to its mates: “Aw-aw, I hear a cyclone coming. You guys staying or going?”

Sciensts have done research on two tropical seabirds, red-footed boobies and great frigate-birds, that live in areas where there are cyclones. They fied tracking devices to some birds so they could see how they behaved when cyclones were approaching. Both these species fly far out to sea to forage for food.

With one cyclone, the birds reacted when the cyclone was 250km away. With another stronger cyclone, the birds reacted when it was 600km away.

The birds on land decided to stay put. Those at sea began to take avoiding acon by flying westward. Cyclones move in a clockwise direcon in the southern hemisphere, so by flying westwards they would be on the edge of the cyclone and able to fly in a circular movement to avoid the eye of the cyclone. They also flew at high altudes to avoid the turbulence closer to the sea surface.

So what alerted the birds to the approaching cyclone hundreds of kilometres away? The researchers cannot say for sure. It could be strong winds preceding the cyclone, or a change in air pressure, or the sound of an approaching cyclone that we cannot hear. Whatever it was, these birds knew it was coming long before any human would.

Oh, and ordinary storms also produce infrasound, so perhaps the terns on the beach today heard a storm approaching while out at sea and came ashore to escape it.

Clever birds.

But how’s this: another study found that trained pigeons could detect malignant tumours in mammograms.

How come birds, which all have small brains, can display such intelligence?

Apparently it’s because their ny brains are packed with neurons –twice as many as the average primate’s brain.

Mmm, I think it’s me we scrapped the derogatory expression “bird brain”, don’t you?