A raw fable about looking up instead of feeling down, “Bird” shows writer-director Andrea Arnold back in a familiar milieu of cramped youth on the periphery, making do with what little is available, seesawing between explosive anger and playful respite. And yet this time, her tale, built around a tough, observant 12-year-old named Bailey (newcomer Nykiya Adams), is shot through with a hopeful streak that feels like a new register for Britain’s doyenne of social realism.

You see it in the exhilarating speed of a motorscooter tearing through blighted and beautiful Kent, and, a little later, in hot-headed Bailey running from the chaos of her life living in a graffiti-strewn squat with her too-young dad Bug (a tatted-out, laddish Barry Keoghan) and seeking acceptance in a roving vigilante gang.

But it’s also present in the luxurious pace of the sweeping Blur ballad “The Universal,” which Bug plays incessantly in lovestruck preparation for his upcoming wedding to a cheery gal, Kayleigh (Frankie Box). She’s plenty friendly but somewhat new to the scene, neither Bailey’s mom nor that of her older brother Hunter (Jason Buda). There’s also a toddler in this ramshackle flat, so be sure to table your judgment about youth raising children from multiple partners. (Then again, you wouldn’t be watching Arnold if your sensibilities were so easily flustered.)

Incessantly, swooping seabirds and crows crowd the sky, following Bailey everywhere, drawing her adoring consideration as subjects of artful phone videos. Are they watchful protectors? Or symbols of freedom for someone rebelling against nuptials she wants no part of? And who can blame her? The bridesmaids are expected to wear a ghastly purple leopard-print jumpsuit. Bailey lets her displeasure be known by having a friend shave off her beautiful spray of kinky hair.

Barry Keoghan in the movie “Bird.”

(Robbie Ryan / Mubi)

Dad’s too preoccupied to fully react, however: Bug is busy trying to pay for the wedding with an exotic toad from Colorado. He’s heard that by exposing it to the perfect cheeseball pop song — upbeat, sincere — it will excrete a natural hallucinogenic: a profitable slime. If there is such a thing as a perfect objective for a Keoghan character, Arnold may have found it. (And all you “Saltburn”-ers, get ready for a cheeky in-joke about one of the song possibilities.)

Bailey’s coming-of-age turbulence begins to ebb when she meets an eccentric, gentle wanderer (Franz Rogowski) in a kilt, who calls himself Bird and whose presence seems to help Bailey coalesce her outsider feelings into an abiding tenderness. Little is explained but much can be guessed about Rogowski’s character, whom the great German actor can’t help but make into a mesmerizing figure of storybook fragility.

Arnold’s work has always naturally drawn comparisons to that legendary chronicler of the downtrodden classes, Ken Loach. But with “Bird,” which deploys the splendid vérité intimacy of her longtime cinematographer Robbie Ryan, Arnold seems intent on explicitly acknowledging a debt to Loach, forging an exuberantly poetic conversation with the director’s boy-and-his-falcon 1969 classic “Kes.” Arnold has made the lingering beauty and vulnerability of the animal world a hallmark of her tales and “Bird” is no exception: There are plenty of other creatures getting close-ups — horses, butterflies, dogs, snakes — besides metaphoric avians and that slimy toad (one that’s really, if you think about it, a mule).

It’s the humans, though, that you’ll remember from the ground up: Adams’ camera-friendly energy and hard-won serenity; Keoghan’s cockeyed warmth, just this side of menacing; Rogowski’s strange, commanding woundedness. If it’s too much to ask of Arnold that her bid for heightened naturalism make a ton of sense, “Bird” at least maintains a heartbeat of ache and affection for youth in all its rudeness, revealing a filmmaker who isn’t afraid of losing her claws if she traffics in the thing with feathers.