Magnus Spence was employed by the Hudson's Bay Company from 1783 onwards, until he retired in 1821 or 1822. His HBC Bio Sheet says that he was born at Birsay in Orkney but the name of his father is not mentioned.
https://www.gov.mb.ca/chc/archives/_docs/hbca/biographical/s/spence...
According to Gary Still, numerous family trees identify Magnus as the son of William Spence and Janet Alleine, but none have provided plausible evidence to support this claim.
https://www.redriverancestry.ca/SPENCE-MAGNUS-1765.php
In my opinion, it is not possible to identify the paternity of Magnus Spence from the Birsay baptismal register, but it is possible that his father, or other relatives, are mentioned in other record sources. If any of my fellow Geni subscribers are aware of the existence of evidence that might be helpful I would be grateful if they would bring it forward.