The use of penicillin in birds has no impact on human health. This is down to two reason: Firstly the UK poultry meat sector uses almost negligible quantities of penicillin (see British Poultry's antibiotic stewardship report).  Secondly, there are strict regulations governing withdrawal period (how much time passes between when any animal is last treated with antibiotics and when it leaves the farm) which ensures that there are no residues in the meat.