For old-fashioned lovers of claymation, “Chicken Run” is 85 minutes of exquisite artistry. The visual effects are both breathtakingly beautiful and hysterically comical. While computer animation is gradually approaching reality’s textured nuances, claymation still has that rough, reach-out-and-touch naturalism.

The movie, which is about a henhouse in revolt, is really a physical comedy. The first 10 minutes are devoted to the hens’ uproarious sequence of elaborate escape attempts from the Tweedy Farm, a 1950s English farm on the edge of automation. The chickens are tired of taking their enforced egg-laying duties lying down, and the opening spoofs “The Great Escape,” with everything from digging under the barbed wire fence with a spoon to an intricate network of underground tunnels. In fact, “Chicken Run” is practically the John Sturges 1963 film, with the iron-fisted, black leather-booted Mrs. Tweedy epitomizing Germanic tyranny.

To escape from Mrs. Tweedy and her oafish, henpecked husband, the chickens have do much more than cross the road (hey, you knew this was coming). They have to surmount a looming fence crowned with twisted barbed wire. The flightless fowls might as well be on a glacial wasteland surrounded by an icy Antarctic ocean.

The indefatigable lead agitator is Ginger (voice by Julia Sawalha, the maligned daughter Saffron in “Absolutely Fabulous”), a sort of Norma Rae or Harriet Tubman with feathers. She’s the ultimate mother hen who refuses to leave any of her fellow chicks behind. Unfortunately, that kind of selflessness gets her tossed again and again into solitary confinement, where she marks the side of her dumpster cell with chicken scratches to count the days.

The situation turns desperate when Mrs. Tweedy, “sick and tired of minuscule profits,” turns to chicken pot pies as a horrifying recipe for success. Hope comes when a circus escapee, Rocky the Flying Rooster, crash-lands on the farm and breaks a wing. Ginger makes a deal with the cocky visitor: a hide-out in exchange for flying lessons. Mel Gibson is the voice of this Rhode Island Yankee in the British courtyard.

“Chicken Run” can’t quite keep up with Aardman’s previous efforts, notably the Wallace & Gromit series and its pioneering genius, “Creature Comforts.” This marks the animation team’s first full-length feature.

Although the film does drag at times, it would be wrong to blame it on the demands of length. The earlier productions didn’t just captivate audiences with their wildly inventive figures and special effects. They satisfied and sustained the viewer with droll dialogue, engagingly clever story lines and believable relationships. Aardman productions are comedies of manners that gently and sweetly satirize fussy human behavioral tics.

There is some of that here, like the plump, oblivious knitter Babs (Jane Horrocks), blowhard militaristic old rooster Fowler (Benjamin Whitrow), engineering Scottish egghead Mac (Lynn Ferguson) and the henpecked Mr. Tweedy (Tony Haygarth). They’re more like quick character sketches, perhaps because the animators feared British wit would go above the thick skulls of Yankees.

“Chicken Run” plays it safe with short-hand pop culture references from “The Great Escape” to “Star Trek.” Still, directors Peter Lord and Nick Park and their incredible studio give so much in terms of the movie’s exquisitely fashioned “cast” and uproarious sight gags that it seems petty to quibble with any flaws. The simple story line should definitely appeal to younger children, and it won’t distract older viewers busy appreciating the Aardman gift of breathing life into clay.

To create this slapstick of plotting chickens, 40 animators guided by the two directors could only get through about 10 seconds of film a day, so no wonder it took four years for this bird to take off. In the cinematic world of instant gratification, though, audiences get an immediate payoff.