They would be the same age in the bird senerio. In the runner senerio, the children of each runner would be the same age within the runner with runners of different ages at from the parent tree, trending towards the direction of least resistance and where ever water was. From my observation, runners tend to run in more or less a straight line whether hemlock or birch. My vote's still with the birds! But then consider for a moment if it was the birds, what kind of birds? - TJ