what bug is attacking aspens?

I was told years ago to cut down my aspens as they won't be worth anything....I did cut maybe a couple of dozen....but now I see many of the remaining aspens are being hammered by the woodpeckers...large chips chewed out of large portions of live trees....some of the trees have broken or blown over....I wonder what bug is in them that the birds are after.

Your aspen are likely dying of old age and are being attacked by the usual fungus and bugs of decay and rot. Aspen usually only live to be about 70-100 years old on average.