Shred the duck and lettuce. Slice the avocados. Soften the tortillas by holding them over a flame; or steam or microwave them briefly. Place the tortillas on plates, and divide the duck, avocado and lettuce among them. Top off with 2 to 3 tablespoons of salsa and a sprinkle of cilantro and peppercorns. Serve with light sour cream or shredded jack cheese.