The mystery of the birds with the weird feet

It’s something that’s bothered me for years. Oh, I forget about it and obsess over other things, like why all the women in CSI Miami have uniformly fabulous long hair when they work with evidence from crime scenes (have they not heard of the scrunchie?) and that weird Moroccan dude who walks around Sandton City in floor-length leather coats. But invariably, something triggers the memory and there I am, wondering again: why do so many of the birds that hang around restaurants have deformed feet?

wagtail
Image source: kemptalk.com

I was sitting at lunch at a restaurant in Ballito this afternoon when I noticed it again. Every single one of the Cape wagtails (Motacilla capensis) flitting about the tables and bobbing in and out of the diners’ feet in search of crumbs had deformed feet. Some were covered in what looked like growths; others appeared to hobble on stumps. It was horrible, especially because I’ve always had a soft spot for these sweet-faced little passerines, with their trusting natures and jaunty little walk. They are fixtures at tea gardens and cafes and coffee shops across South Africa – but clearly something is very wrong.

Back when I first noticed the deformed feet of the wagtails, at Wits where I was studying drama at the time and eating far more Chelsea buns than was strictly good for my BMI, I assumed it was somehow caused by urban pollution or – during my wilder flights of fancy – a local source of radiation that was causing the birds to mutate. Possibly Wits had a local equivalent of Pinky and the Brain lurking in one of its labs. It was creepy.

As it turns out, many others have observed the same thing. In fact, as far back as the 30s, a Rev Robert Godfrey wrote: “In Cape Town, as in East London, the city wagtails are liable to some mysterious disease of the feet …”

Several reasons have been advanced for this strange phenomenon:

• Pesticides in gardens
• Parasites – mites can cause encrustations when they get under the scales of the feet
• Junk food (the birds hang around fast food joints after all)
• Thread winding around the feet and cutting off circulation
• Polluted streams – wagtails are waders and often feed in or near water

Professor Steven Piper, the ornithologist quoted there, mentions removing thread from the feet of birds in a study. He also suggests that pollution in urban streams may be a contributing cause, because only birds in urban areas seem to suffer from the problem. But he dismisses pesticides in the food chain, arguing that other birds would show the same symptoms if this was the culprit.

In fact, the most likely explanation is a parasitic infection. That was the finding of Tracy Munday, who wrote her MA thesis on foot deformities in wagtails. Her hypothesis, that the deformities were linked to environmental pollution, turned out to be wrong. While she found that some birds were affected by thread wound around their feet, for the most part, deformities seemed to be caused by the Scaly-leg mite, which causes a disease known as knemidokoptic mange (remember that for your next game of Scrabble).

So there you go. It isn’t pollution, it isn’t Pinky and the Brain. It’s mites. A rather disappointingly prosaic conclusion to a mystery I’ve pondered on and off for nearly two decades. Why Cape wagtails should be so susceptible isn’t clear. But next time you see one hobbling around your feet while you eat your sarmie, leave the poor thing a crumb or two. It could probably do with the help.