When the Pine Martens and Buzzards started to increase their territories in Ireland from the 90s onwards there was a noticeable decrease in grey squirrel population. In fact the buzzards got the credit first as they were more noticeable.
What was pleasantly surprising was how quickly the red squirrels reappeared, albeit in very low numbers. The likes of the National Parks and Wildlife Service were very slow to credit the buzzards and martens with reducing the greys. I couldn't put my finger on the exact date but years earlier they sponsored a PhD student who concluded that grey squirrels were not a threat to trees.
I've seen at first hand the marten damage to release pens and poultry from the late 80's. This was from a population that was spreading naturally.
I believe that even in Ireland there were relocations by NPWS.
In the 80's I saw martens in Wicklow, and they were widespread on the west coast.
When they have finished off the grey squirrels easy pickings, it's natural that they turn their attention to the next easy prey.
In the much missed Stalking magazine I think it was Struthan Robertson who wrote about the depradations of the Marten in the Highlands. That would have been the 90's?
