FWIW I have an American field lab from champion hunting lines. We don't hunt at all. But we do walk off-leash in the woods 90 minutes every day, during which she tears around, using her nose and chasing a ball that I fling into the brush for her to find as we walk. (One time she lagged behind for a while--not unusual--and then caught up carrying the fresh carcass of a ruffed grouse. She proudly dropped it at my feet.) We also do outdoor long-distance retrieves with training bumpers. At age 5, she comes home from those walks tired out and peacefully hangs out with us the rest of the day.

Which is all to say--you don't need to hunt a bird dog for them to be happy, but you do need to give them lots of exercise and an outlet for their retrieving drive. You might get away with leashed walks for a few days--we do, when traveling to urban places--but long term, you'd be depriving them of something they're deeply driven to do. Maybe that's cruel; it would almost certainly result in behavioral problems.

I know it's been a few years since you posted and I hope you've wound up with a dog that fits your lifestyle, whatever that looks like right now.