Combine garlic and ginger in food processor fitted with metal blade.
Process until finely chopped.
Add yogurt, spices and salt. Pulse to combine.
Place birds in large glass or ceramic bowl.
Add yogurt mixture and rub over birds inside and out.
Cover and refrigerate 24 hours, turning occasionally.
Preheat oven to 400 degrees.
Set birds on rack in roasting pan and spoon marinade over them.
Roast until internal temperature of thigh reaches 180 degrees (about 45 to 55 minutes) .
Let stand 5 minutes before serving.