I use a modified sous vide method for this, as it uses less fat than submerging the pheasant legs in 4 to 5 cups of fat or oil. I save up chicken fat or pheasant fat and combine it with butter, but you could also use lard or olive oil. I don't recommend using duck fat, which is traditional with confit, because I don't want a ducky flavor with upland birds. But if this doesn't bother you, go for it. Of course you can use this technique with lots of animals, and I find these flavors work well with any chicken-like bird: Chickens of course, but also turkeys, grouse, quail and partridges.
Once made, this confit will last — sealed in its bag — for a month. It can also be frozen for up to a year.