The Irish Setter, like all Setters, was originally developed as a "gundog", that is to say a breed used in hunting small game, usually birds. Unlike other hunting dogs such as terriers who give chase and kill the prey themselves, the Irish Setter was always intended to hunt in conjunction with a human companion. On a hunt, the Irish Setter will use his or her keen sense of smell to track prey. Once they find the type they're looking for, instead of chasing, the Irish Setter will adopt a frozen stance that simply and silently points the direction towards the prey for the human hunter to pursue. This posture, called "setting" the direction of a quarry, is where the breed gets their name.
Although most Irish Setters today are kept simply as pets and companions or as show dogs, their hunting instincts are still very much a part of the breed and thus they can still be employed as valuable resources in the field. If you're looking to use an Irish Setter as a hunting dog, however, there are several points that you'll want to keep in mind.
Firstly, be aware that there are two different "stocks" of Irish Setter available. The first of these are show stock, which means that they're bred to emphasize the more aesthetically pleasing aspects of the breed, such as their rich, flowing coat and larger size. Conversely, there are also work stock litters, in which the puppies are bred for those attributes that make them better hunters. In general, work stock Irish Setters will be smaller and have shorter coats as well. Since it's unlikely that an Irish Setter employed mainly as a hunting dog will be seeing much of the show ring, it's not necessary that they maintain the same long coat as their show counterparts, and in fact this can even become something of a detriment as frequent walking through brush and woods will grant many opportunities for a longer coat to tangle and mat. When choosing an Irish Setter puppy to be used as a hunting dog it's advisable to seek out a work stock litter.
Once you locate a suitable litter, try and find a puppy who shows a natural excitement towards or interest in birds. This is a good indication that the dog retains much of his instinct for hunting and is a highly prized trait among hunting dogs.
Training and obedience should be carried out as with any other Irish Setter, but with the obvious introduction of tracking and dealing with birds. Once the Setter has learned basic commands such as stopping and staying, he or she can be allowed to track domesticated pigeons by scent, but must be prevented from giving chase with a firm command. This is actually easier than it sounds thanks to the breed's history and it shouldn't take considerably more effort than any other specialized training you might undertake with your dog. Once the Irish Setter has learned to set direction rather than give chase, you can begin to develop his or her senses to a greater extent by teaching them to track through more difficult terrain such as wetlands.
Though the Irish Setter tradition has become that of a pet or show dog in modern times, there is no reason that the traditional use of the breed can't be harnessed and put to good effect. In fact, some of the strongest performers in field trials and hunt tests have been Irish Setters. Keep that in mind when training an Irish Setter for the field, and never give up.