As I promised in the past post, here is a description of what "hacking" is, for those who are unfamiliar with the word. It is a term that is originally from falconry and is a method for soft release, usually of a young preflighted bird.
In the case of the osprey reintroduction, we collected young ospreys from northern Minnesota at about 5to 6 weeks of age. At that time they are old enough to know they are ospreys ( no threat of imprinting) but cannot fly. They were put into "hack boxes", which were large 6'x6' boxes with hardware cloth around the outside and a roof on top.This served to protect them from predators  The boxes were placed high on some scaffolding to simulate their natural nesting habitat. We built a nest inside the box for the chicks to lay in. They were hand fed twice each day and they spent time looking out at the world surrounding them to become aclimated to their new home.  They exercised their wings and learned to rip and tear a whole fish. As they began to show the developmental signs of being ready to fly we originally opened one side of the box for them to fly. This unfortunately left the ones who were not ready vulnerable to predation. So I developed a way to release them individually by taking them to the roof of the box in a box or duffle bag and we let them slowly step out of the box. We had perches up there for them and a big plate full of fish so they understood that this was the place to return to for food. It worked every time. They would sit for a while and eventually take flight when ready. They returned to eat several times a day and would often congregate on top of the box and food beg. I was one of the hack site attendants, and the sound of that chorus of hungry young ospreys was a delight to hear as I rounded the bend with a 5 gallon pail of fish for them.Ospreys will return to the place where they learned to fly when ready to breed. This is the process that was used to restore Ospreys as a nesting species to the Twin Cities.  Most of the birds on our nests now are wild hatched but there is still one hacked male alive at 19 years of age.