The London winter sun is so slow and sleepy these days. It barely creeps out of bed by 9:30, casting a half-hearted greyness across the rooftops. It can hardly stay awake til 4:00 in the afternoon, when it sinks back exhausted into its bed of clouds the color of minor bruises. When it does manage to open its eye a crack, though, it’s quite a show, igniting the sodden hillsides of Hampstead Heath with a deep, fulgent glow. Everything seems to burn intensely for a moment, like a black-and-white film that suddenly bursts into color, before the sun winks out again and the park and its perambulators return to the old chromatic monotone.

I was walking through the Heath the other day with my son and his friend when my son’s friend mentioned that he and his family had seen parrots here. Parrots? That’s not possible, I thought. There are no parrots on Hampstead Heath. “Are you sure?” I asked. He was sure, but I still didn’t believe him, thinking he must have mistaken some other birds for parrots. Then, a few minutes later, and a few hundred meters further down the Heath, my son shouted: “There they are, Dad!” I looked up and sure enough, there in the branches above my head were two bright green parrots. “Wow,” I said, “I never knew there were parrots on Hampstead Heath.”

As incongruous as it seems, there are indeed parrots on Hampstead Heath. In fact, they’ve been spotted in parks and gardens all across London. There are some great explanations for their presence here, too. One theory goes that the parrot population is descended from birds that escaped from the set of The African Queen, which was apparently filmed in studios outside London. Another hypothesis is that the birds are the progeny of Jimi Hendrix’s parrots, which are supposed to have flown the coop after the singer’s death in London. So far, no one has suggested that the famous Monty Python “parrot sketch” has anything to do with the phenomenon. Whatever the truth, it’s pretty startling to see such birds in London, hardly even a close approximation of their native habitat. I had a good long look at the birds, musing that their appearance here was a pedestrian example of the ‘uncanny’, and continued the walk with my son and his friend.

Finding something ‘uncanny’ always involves a mix of the strange and the familiar: something quite ordinary is sharply transformed into something exotic, bizarre or spooky. The presence of two parrots transforms Hampstead Heath into a rain forest; or the parrots themselves are transformed into numinous messengers from another world. Sigmund Freud wrote a fascinating essay on the uncanny, saying the experience “derives its terror not from something externally alien or unknown but—on the contrary—from something strangely familiar which defeats our efforts to separate ourselves from it.”

The uncanny is not necessarily always terrifying, but it is always unsettling. Some of my own experiences of the uncanny were certainly like that. Once, at a train station, I watched a collapsed wheelchair go up an escalator all by itself. There was no one in the wheelchair or even near it, so I had no idea how it got on the escalator in the first place; a very weird sight. Also, one evening when I was coming home from work, I turned a corner and saw that a street near my house was completely flooded from a burst water main. The whole street was transformed into a briskly flowing river, everywhere about an ankle deep. Very strange and scary to see a street transformed from one sort of thoroughfare to another, and frightening to see the force with which the water swept down the street.

Johann Wolfgang von Goethe has an aphorism about rainbows—an uncanny experience that is inspiring rather than terrifying—that gets at the simultaneous attraction and repulsion we feel toward the out-of-the-ordinary:

When a rainbow has lasted as long as a quarter of an hour we stop looking at it.

We all marvel, or tremble, at the uncanny, but it makes us bored or uncomfortable if it goes on too long. Rainbows are gorgeous, exciting things, but their fame (like our own) is limited to about 15 minutes. Those parrots piqued my curiosity, but shortly thereafter I continued my walk, eager to get home. The uncanny has an extremely short half life. That’s no bad thing, I think. Intense experience are, by definition, brief—and are all the more intense for being so. Earthquakes are also uncanny. I was in quite a few when I lived in San Francisco. The earth moved for only a few seconds, but I was left permanently rattled.