[Macbev]

Can't quote any stats here as I didn't bother to collect them at the time, but when I was trawling parish baptisms,(RC) illegitimate births were shown as such. State registration of births did not occur until 1864, if I remember correctly but certainly there seemed to be a more casual attitude towards it than in the UK. My OH's grandfather, born in Donegal, was baptized (Presbyterian) several months before his aunt got around to registering the birth....and then fudged the date of birth (to avoid the fine, I think)
By and large, the Irish considered baptism of far more importance than registration. I have found baptismal records for each of my Ryans from Tipperary, but few were registered.