Quail are considered Poultry because they're of the superorder Galloanserae members.
And Poultry is essentially animals or birds kept by humans for meat and eggs so Quail are certainly Poultry because they're actually birds.
Any birds that are kept by humans for food or pets are considered poultry including the turkeys and chickens and quails.
Quail is also very good tasting meat and seems to taste better than chicken in my opinion.