Our hens would occasionally do that when they are broody or waiting for the right moment to 'settle down an start nesting'.
I'm pretty sure it's an instinctual (if that's a word!) thing they grasp from birds as a whole. Basically collecting materials for their nests and babies.
I love to watch it. When my Polish hen was laying for the first time, she was collecting like crazy! She would walk from the coop to outside and just walk around with leaves and other small items on her back, go back to the nest, drop off whatever stayed in place, and go hunting for more. She'd even go after really bright looking pieces of garbage she found outside. So cute and very funny. They'd be in a trance as they were doing it and I'd hand them materials, which the girls would take and place right on their back or in place in their nests.
I'm pretty sure it's an instinctual (if that's a word!) thing they grasp from birds as a whole. Basically collecting materials for their nests and babies.
