Upon the hill

Where do all those rivers run Which take so many far from here? Some leave for a day or two While others seem to go for years. As I watch the waters flow I feel a certain type of chill, For I don't know the answer And I am sure I never will. Now, where do all the birds go That catch a ride on thermals high? Seem they disappear so quick With quite a sound as they pass by. Some will return in the spring Yet there's a few I'll never see, And for those now lost in time, They're a mystery to me. I sit through every season And I change with the weather too; I've watched old ones pass away While mothers bring in life anew. Day and night, through rain and snow, Often saved from the lumber mill; For eighty years I'm the tree That sits alone upon the hill.