From: "Carrol Cowan" > O.k., it isn't really hiking, but you can get your
heart rate up on the towpath if you work at it.

The preferred way of working up cardiovascularly on the C&O is on a bike. I
once counted 12 singing prothonotary males in a 9-mile stretch doing that.
Unfortunately birding by bike is just like hiking - you stop too much to get
any good out of it.
    Is it possible to hear a prothonotary without trying to find it
visually? They're like so many other warblers - too pretty to pass by.
    Jerry