At just over 3 weeks old they can feed themselves some quicker than others some slower of course , at no point would anyone remove a yb from there parents if weren't fit to fend for themselves , but obviously D.E.F.A has got it wrong yet again but then again most of there information will be from vets / unions and the head of one been from the old pals club and not a racing man no wonder this vaccination / sales information is sketchy and may need further research by DEFRA , imo 2 months old would be soon enough to Vaccinate ybs , and why does this only apply to Racing birds theres nothing covering fancy birds at sales from what i understand , these be more risk than the offspring of vaccinated birds which would have some immunity from there parents