It could be a case that the birth wasn't registered.
However, I found these baptisms on the liverpoolhistoryprojects website for St Winifred Bootle
Year of Birth
Year of Baptism
Forename of Father
Surname of Father (if different)
Forename of Mother
Maiden Name of Mother
For Full Details of this Baptism
If they are the baptisms of Patrick's sisters, notice the mother's maiden name as Burns, it could be that Mary's mother was Burns and perhaps re-married McQuaid.
I found this marriage 1877 Lancsbmd
Lancashire Marriage indexes for the years: 1877
Church / Register Office
West Derby, Register Office or Registrar Attended
The marriage took place at St James Bootle (info from liverpoolhistoryprojects website.
For Full Details of this Marriage
ST JAMES BOOTLE
If you go to the website http://www.liverpoolhistoryprojects.co. ... riages.php
and find the baptisms and the marriage, you can click on where it says request form and request the actual entries taken from the parish records I think they are about £3 each or all 3 for £10 or alternatively the records are on film reels at Liverpool Records Office or Crosby Library, you can get the print outs from the film reels for about £1 each.
Margaret Alice Riley's birth reg
Margaret Alice Riley
Parishes for this Registration District:
View Ecclesiastical Parishes associated with this Registration District
It may be worth getting a copy of Margaret's birth cert to confirm parents and the address and try and match it up to census records.
Old genealogists never die......they just lose their census.