For the past 2 years I have done a darkness system where by I darken the birds early MAY for ONLY 4 weeks. The birds will carry on with a fairly normal moult of their primary flights, but go through a complete body moult. ADVANTAGES - less time on the system - birds can be flown out in early summer evenings and mornings, not sitting in dark - body feathers in good condition throught racing - birds cast all primaries by end of autumn, no lights needed to push moult. DISADVANTAGE - primary flights missing during racing season.