work of the Pileated Woodpecker

Why so many and so low down, these are not prospective nest sites? Food sources? Mating behaviour?

no this is purely a food source, M. The reason I know it's a pileated wp...is because of the size of the chips present on the ground. I have seen a pair of these birds take a tree totally to pieces. This tree remains viable even though the holes are on all sides of the tree.. the base has been infested with carpenter ants which the pillies love. It won't be long until the tree dies, unfortunately. It's hard to tell exactly but there is an entrance wound of some type visible in this picture. It is possible that it has succumbed to an infestation of something other than ants, as the Ash (emerald ash borer), Maples (maple borer), Abies (bud worm) and Elms (Dutch Elm Disease) have been threatened over the last 30-50 years. There is a fungus disease that started in the U.S. and has spread eastward across N.A. only just reaching us this year...it's white fuzzy looking masses on the underside of new growth. Our forests are under seige.

Dire prospect, yet more trees under threat!