Further to all of the above and per JMStrachan, Duncan appears in the 1861 Census in the next village of Tapul (Tavool).
I believe that this is the correct Duncan, simply because it has to be.
1861 Kilfinichen & Kilvickeon District 1 Page 4 Tapul House
McPhail Ann 25 Head Farmer of 3000 acres Argyllshire Torosay
McPhail Mary 17 Sister Housekeeper Argyllshire Torosay
McGillivary John 39 Servant Shepherd Argyllshire Kilfinichen
McPherson Donald 19 Servant Shepherd Argyllshire Kilmore
McLauchlin Lachlan 19 Servant Ploughman Argyllshire Movern
McLaine Margaret 23 Servant Domestic Servant Argyllshire Kilfinichen
McGillivary Duncan 9 Servant Cowherd Argyllshire Torosay ****
Burg was part of Torosay parish before it was included within Kilfinichen and Kilvickeon.
Although his age is 9, this probably means in his ninth year, so actually 8. This fits very well with brother Malcolm 1851, Duncan 1853 and Alexander 1856.
I have Duncan's parents, grandparents and G-grandparents details on site.
Michael (webmaster)
http://mullfamilies.co.uk/