In the 50s I only spoke Lowland Scots but I (now) speak Danish and German and, coupled with Lowland Scots, this fourth verse posted above can be understood instantly by me (and also by a Dutch friend of mine):

syn wite hals is dy ta bút
ik pik syn blauwe eagen út
in lokke fan syn gouden hier
is foar ús nêst in tek en sier
is foar ús nêst in tek en sier

I think when the lines are spoken, for example 'eagen' pronounced with the 'g' softened sounds like 'een' in Scots ('eyes' in English) and other examples taken from the verses would show that Dutch/Flemish speakers would understand a great deal. The connection between Dutch/Flemish/Platt-Deutsch is very close: the German word for eyes, for example, is 'augen' (hard 'g').