it can be even earlier mate, all depends on the pairs themselves ive had pairs go down before the young birds were even 15 days old, so it depends on the pairs themselves and myself personally wouldnt be able to tell you the exact day, but i defaintly know most of my pairs go down before the young birds are 20 days as i wean at 21-23 days and most of the time the parents are already on there second round of eggs