You hear them long before you see them.

They announce their pending arrival like the blare of an ambulance giving you warning from blocks away — a distant peal growing louder and louder until you can't ignore it any longer.

When you look up from your TV, your newspaper, iPad or smart phone, you realize just how incongruous the sound is. It doesn't belong in the city, unlike the siren, or even the thumping of helicopter blades overhead.

It's a call that belongs in the jungles of Central or South America. Or in Madagascar. When I close my eyes and try to put an image to the noise, it reminds me of marbles colliding, thousands and thousands continuously crashing together in high-pitched warbles.

It's the sound of exotic birds taking over the sky.

Parrots have invaded Burbank.

First you hear one far away, then two, then scores, until the air is filled with their unmistakable chatter before you've caught sight of them. Their collective voice builds and builds as equal measures of fear and excitement swell within you; you wait to see what makes such a din.

From nowhere, everywhere and elsewhere, over rooftops, trees and telephone wires, your anticipation is rewarded as aquamarine fliers overrun the sky. They speed across the blue, street by street, neighborhood by neighborhood, heading I know not where. Watching them, it seems even they don't know where they are going, flying this way and that, from every angle and in every direction.

They are a loosely synchronized chaos of clamor, feathers and neon green.

They aren't new, though. Flocks of non-native parrots have been spotted across the area for decades. There is no one factual record of their origins. Some sources trace them back to escapees from the tropical Busch Gardens theme park that called Van Nuys home from 1966 to 1979. Or farther back, to a nursery and bird farm fire in Pasadena.

Others claim they've simply migrated north from Mexico.

With Southern California's balmy weather and abundant sources of food, they've survived and thrived in small populations of their own, much like the rest of us who call the Los Angeles area home.

As probable as the stories sound, I like to think these alien residents came to us by more romantic, intentional means. I imagine a sage, eclectic and inspired Angeleno long ago in troubled times opening the cages of her beloved companions, too tired and pained to see them captive any longer. And with her dying, hopeful breath pouring out her wishes for them, the world and us.

“Be free.”

And her wish multiplied and thrived.

Their descendants, in numbers too great now to hide, swoop in to invade every corner of our cities, one by one, when called by some unknown spirit.

As quickly as they come, they fade away and the skies are silent once more, leaving you to wonder if the phenomenon of their appearance was a fluke. Have they gone forever? Will we ever hear or see them again?

When they move on to terrorize and amaze another neighborhood, it's hard to tell whether they are fleeing, or, work done, simply departing, speeding quickly to their next destination with a great urgency and purpose even they don't yet know.

And when they come back — always, they return — you're just as surprised and mesmerized as the first time, marveling at their incompatible sight once more.

Are they an omen? A sign of global warming? Nature's wrath come to reclaim what is rightfully hers?

Or is it but one more piece of dross to gossip and tweet about, like Angelina Jolie's right leg?

My bet is they are just another odd sight in a city with all too many of those. I'm glad to have the distraction, though. In these times, when we're all a little messed up, when the world moves before us in hazy frustration, it's nice to have the disruption of a thousand emerald criers piercing the self-made bubble of our isolation, offering momentary freedom from our own cages of addictions to money, pride, fame, fear, anger and self-destruction.

They remind us of something better, of hope, our destiny and purpose; a glorious green and small wonder pleading for attention in a world gone gray and amok.

Look to the skies, folks. They'll be there.

PATRICK CANEDAY is the author of “Crooked Little Birdhouse.” Friend him on Facebook. Contact him at patrickcaneday@gmail.com. Read more at www.patrickcaneday.com.