This bird is anything but a featherweight.

When a British animal sanctuary discovered a small, wet owl unable to fly, experts initially assumed the corpulent critter was waterlogged or injured. After weighing her, though, they discovered she was just an incredibly fat fowl.

“This soggy little owl was found in a ditch a few weeks ago,” the Suffolk Owl Sanctuary wrote in a blog post titled “A not so little, little owl,” which has since gone viral around the globe. “When we examined her, we found her to simply be extremely obese!”

The hefty birdbrain — nicknamed Plump — weighed in at a “chunky” 245 grams (8.6 ounces) — about a third heavier than a healthy female little owl ought to weigh, the sanctuary writes. Her extra chub had rendered her flightless: “[She] was unable to fly effectively due to the fatty deposits around her body,” the post explains.

Being too fat to fly is “extremely unusual for wild birds,” so the sanctuary investigated. After ruling out that the chonk of an owl was an escaped aviary bird, they put her under observation and determined that “this may just be an unusual case of natural obesity!”

Due to a particularly warm and wet December, the plump bird had far more prey to feast on than usual — and had made the most of it.

“Where she was found is very productive land, and it’s been a mild winter and there’s a lot of food around — voles, mice,” the sanctuary’s head falconer, Rufus Samkin, tells the BBC.

Her weight gain was “quite exceptional, as most birds we see are starving,” Samkin tells NBC News. “She absolutely gorged herself and got very fat. She had a lovely time — but went too far.”

Plump was promptly put on a “strict diet” to slim down to a more “natural weight.” Sanctuary staff also encouraged her to exercise in the rehab center by feeding her low to the ground.

She eventually lost between 20 and 30 grams (.07-1.1 ounces) over two and a half weeks.

“We can now happily say she has trimmed down to a more natural weight for release,” the Suffolk Owl Sanctuary post concludes.

“We may see her again — we hope not,” Samkin says, before staffers let their “little star” fly off into the wild. “Hopefully, she’s learned to keep her weight in trim so she can escape any predators or being picked up.”