When the penguins moved in around 25 years ago the locals of Simons Town wanted them to be evicted. The din they make when all gathered in the evening can sound like 1,000 donkeys being stabbed with sharp sticks. So why has Boulders Beach, home to about 2,500 refugee African penguins, become one of Cape Town’s top five tourist attractions?

Okay, so they are endearing little things, all short-legged and in black-tie, waddling up and down the beach like avian Charlie Chaplins. They can dive to 130 metres (350 feet) and their feathers act like biological wetsuits keeping them warm in sub-freezing water.

But, being flightless birds, they usually avoid nesting on mainlands where they are helpless against land predators. So why do they nest and breed – rather successfully – at Boulders, which is very much part of the African mainland?

The main reason is that they need to dig nests to protect their eggs, and in times past all the islands off the south and west coast of Africa were covered in deep coatings of guano (bird poop) into which they dug their nests. Then those islands were stripped of the guano to make gunpowder and fertiliser and the penguins were in poop of a different kind.

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At Boulders in Simons Town, and a few other places on the South African coast, they have found save havens where they can dig their nests into the soft beach sand and sea-facing dunes, where land predators cannot get at them. It is true there are a few mongooses in the area but otherwise they are surrounded mostly by holiday homes where there are no pets.

There is no other mainland on Earth where you can see these fascinating, land- and water-bound members of the flying classes without having to don polar gear.