Looking at the 1881 census, son's name is James, not David.


Marriage: Ancestry.ca

James Mason, 21, b Canada, living Glandford, s/o Joseph & Rebecca Mason, married Mary Ann Burk, 20, b Canada, living Onondaga, d/o Francis & Elizabeth, witn: Annie Bethune of Walpole & Maggie Black of Manitoba, 26 Jun 1872. Seneca, Haldimand.





Birth: Ancestry.ca

Rebecca Mason, 26 Dec 1872, parents: James Mason & Mary Ann Burke, farmer, Informant; James Mason, farmer, of Glanford, Wentworth County, Registration# 025485.

Edith Mabel Sabina, 16 Apr 1886, James Mason & Mary Ann Burke, Puslinch, Wellington County, #038942.
They must have moved to Wellington County.

1851 census Glandford, Wentworth County

MASON
Joseph, cooper, b CE, 72
Rebecca, b USA, 57
Thomas, cooper, b CW, 38 widowed
Alex, b CW, 18, laborer
Rebecca, b CW, 23
Elizabeth, b CW, 16
James, b CW, 14
THere are no relationships given on this census.
CE=Quebec
CW=Ontario
There is also a Joseph Mason, farmer, b CW, widowed, aged 26 and
Elizabeth Ann Cobbs, b England, 5.
He could be living next door or maybe they are all living together.
No separation between families. Names just go on and on.

You can order any census from the LDS library or your local library. 1891 in Puschlinch, Wellington might be worth a look.