The blue swallows of Kaapsehoop swoop over the high grassy plains near to the town every summer. Their lovely, dark blue, metallic feathers gleam in the sunlight. But in terms of birding, they are a challenge – there are only a few dozen of them left, mostly found in Mpumalanga.

But this beauty hovers on the brink of extinction. Every spring, birders report with relief that the blue swallows have appeared again, having successfully made it through their long migration from the highlands of Malawi, Zambia, Uganda and Tanzania, where they overwinter in mild climes.

Blue swallows are superbly adapted to very specific environments – high-rainfall, high-altitude grasslands that are frequently shrouded in mist.

Unfortunately, these very ecosystems were targeted decades ago by forestry companies wanting to plant pine and eucalyptus plantations. It was done at a time when grasslands were simply not recognised as the important, biodiverse regions as they are now. As a result, pristine mist-belt grasslands are at a premium for these birds. Their habitat has just been eroded away by development.

In South Africa there are fewer than 80 pairs of blue swallows left, and they are scattered in little pockets around Mpumalanga, making them something of a birding challenge. But they have a stronghold around Kaapsehoop, and breeding pairs can be spotted in the Blue Swallow Reserve, a 460ha natural heritage site.

Their nesting habits are quite unusual. They make a cupped nest in a deep depression, ditch or aardvark hole. Around the old gold-mining town of Kaapsehoop, they nest in abandoned prospecting and mine shafts

More than 60 percent of South Africa’s grasslands have been transformed by forestry or agriculture, and blue swallows are now seen in some circles as eloquent avian ambassadors for this threatened and previously under-appreciated ecosystem. The Endangered Wildlife Trust has recognised this ecosystem, for example, through its Threatened Grassland Species Programme.

Guides at Kaapsehoop have been trained to take birders to the right places, but these birds are sometimes difficult to find.

Of all the avian migrants that visit South Africa every year, the blue swallows that visit Kaapsehoop must surely be one of the most beautiful. A dark, iridescent blue with flamboyantly long tail feathers on the males, this swallow hawks above high-altitude grasslands, catching insects on the fly.