I agree with Bleckie I have this in my own Perthshire lines Patrick suddenly became Peter directly after the 1745!!

Having a look at the parish map for Perth gives you a better idea of how close Monzie and Fowlis Wester actually were.
http://www.scotlandsfamily.com/parish-map-perth.htmThe batch numbers on the IGI for Monzie give a clear indiction of the numbers of McAras [births and marriages] on the microfilm for that parish.
C113822 Monzie births 1720 - 1825 144 McAra births
M113822 Monzie marriages 1700 - 1706
M113822 Monzie marriages 1728 - 1821
C113572 Fowlis Wester births 1674 - 1819 48 McAra births
M113572 Fowlis Wester marriages 1674 - 1819
M113424 Crieff marriages 1748 - 1819
M113466 Dull marriages 1783 - 1820
and of course there were marriages in other parishes also.
Marriage
usually took place in the brides parish and the newly wed couple set up home in the grooms parish. Often the bride would return to her [mother] parish for the birth of the first child hence the reason children are sometimes not born in the parish they grew up in.