Hi,
Are you sure you have the correct Frederick on the 1911 census?
I am fairly sure that he married Elizabeth Ann Bratt at St Lukes Salford and his father was named as Robert Birch, Moulder:
Marriage: 6 Aug 1906 St Luke, Weaste, Lancashire, England
Frederic Birch - 38 years Seaman Widower of 32 Leopold St.
Elizabeth Ann Bratt - 35 years Spinster of 32 Leopold St.
Groom's Father: Robert Birch, Moulder
Bride's Father: William Bratt, (deceased), Jeweller
Witness: Fred Hargreaves; Rose Flear
Married by Banns by: W. L. Cottrell
Mo