Jon Beresford, one of BAR's founders, said finding a peregrine on the ground was unusual.
"Unlike the vast majority of birds, when they fledge they don't land on the ground, they have short flights from the nest and they go back to the nest.
"So somehow she was found grounded and injured.
"So I suspect during her first trips from the nest flying, she's come a cropper, she's hit something," he said.
It was found the bird was the offspring of a male peregrine successfully treated by BAR last year.
But the shelter did not have the facilities for a young bird to continue to learn to fly, so it was taken to an aviary at Leicestershire Wildlife Hospital.
Beresford said all the effort was worth it when the falcon had recovered.
"It's a privilege not only to treat such a magnificent bird as a peregrine falcon, but also to release her and see her fly again so well."
After hearing "some squawks", she found her parents and siblings.
"It really brought tears to our eyes," said Beresford.
