Well it is Irelands rarest animal Neil!
Simple answer, they aint too concerned about balance. Before the gray squirrel, red squirrel was a big part of the PM's diet, and when and where the the grey is gone, the red will be back under a different type of preasure.
Feckin egits thinkin the marten is running around chasing squirrels in the tree's. He's a clever boy! He'll take them at night. He has good eyesight, and the upper hand at night like most predators. Even roosting birds aint safe with this predator. I have to say i admire his skills, but at the same time im well aware of the fact that he is very destructive when numbers are too high. And they certainly are for most parts of the country.