Great Gray Owls are very large birds that feed, oddly enough, on rather small prey. Here are some facts on these owls that might help you capture that photograph.
Want to know how to photograph Great Gray Owls? Tip one - find them at home. Broken-topped dead trees or existing nest of other bird species are your best bet.
The young usually leave the nest around 26-28 days. Which is probably best, because the mums have had it by then. Owl parents split their roles differently - mum will stick around for a while and protect her fledglings as their learn to fly, which if you haven't seen it for yourself, is kinda' hilarious. (It usually takes a week or two to figure out how the whole flying-thing works.) Dad watches over the kids even longer, offering food.
The location of this family was in Alberta, Canada. You can find these birds on the prairie, usually searching for food, but they prefer the forest. I can report having the best luck observing great gray owls in May and June. When their owlets look like fluffy muppets.
There isn't a lot of bird under all those feathers. Snowy owls have larger talons, and other owls are heavier. The best example I've found for how little of "bird" is under all that face goes to FunkMonk.
Feel free to use my photographs for whatever you want. You can download them from my account here: pixabay
Because you don't have to take my word for it.
US Forest Service. http://www.nrs.fs.fed.us/pubs/gtr/gtr_nc190/gtr_nc190_498.pdf
US Forest Service. http://www.fs.fed.us/database/feis/animals/bird/stne/all.html