Hens and roosters don’t fly

That isn’t completely true. The wild ancestors of our chickens needed flight as part of their survival strategy.

The different breeds of chicken that still exist today have varying degrees of ability. In general they aren’t good or persistent fliers. Of course humans are at fault. They kept and bred chicken for meat and egg production. That’s why chicken mostly kept or developed even bigger muscles but their wingspan didn’t keep up with their body weight. Smaller breeds with regular feathers can fly a short distance and reach a height of about 9 to 10 meters. That’s why my grandfather regularly clipped the wings of his chickens and still had a high fence surrounding the area he kept them in. The chickens were still able to fly up into the small bushes and trees.