It seems an important fire had broken out at the level of the intrados (under surface) of the left wing.

CNN: graphic

But Dr Dial wanted to be sure, so he compared the accomplishments of normal partridges with birds that had their wing feathers clipped to half their normal surface area, and to even less fortunate fowl whose main flight feathers were entirely plucked.

ECONOMIST: Birds that don't fly may be using their wings to run uphill

Instead of moving a physical surface, fluidic controls divert the airflow over a wing by blowing compressed air out of narrow slots.

ECONOMIST: How to fly without ailerons

Wing strokes press the animal towards the ramp and help the bird stick to the surface rather than slipping over it.

ECONOMIST: Birds that don't fly may be using their wings to run uphill

Handmade from the tough bark of the Tara Wing-Celtis or Blue Sandalwood tree and rice straw, Xuan paper is known for its strong, smooth surface, its ability to absorb water and moisten ink, and fold repeatedly without breaking.

UNESCO: Culture