I notice that this query has been explored previously.
In the interests of avoiding duplication of effort, see:
http://www.rootschat.com/forum/index.php/topic,229301.0.htmlmarhat, Where did you get information that Thomas was born in Ayrshire?
I note that there are some (I would say extremely unreliable)
LDS submissions in the IGI as follows:
Thomas BICKERSTAFF b 1805 Scotland, m Ann 1830 Birmingham Warwick
Thomas BICKERSTAFF b about 1806 Ayr Scotland, d 1890 (! - I note that Ann was a widow in 1881 and possibly/probably earlier)
Unless you have found mention of Ayr elsewhere, it would be very unsafe to rely on the above submission.
Incidentally, are you sure that the 1828 marriage is the correct marriage? I guess to ensure that this is the case, you would need to get a birth certificate for a child born after statutory registration began (David? - presumably David BICKERSTAFF, birth, Jun qtr 1846, Birmingham, Volume 16, Page 288) as that should show Ann's maiden surname.
And we really need the answers to the following questions:
1. In which censuses have you found Thomas?
2. What is his birthplace in those censuses?
Regards and good luck,
JAP