While kayaking a spring flooded grass and timber bottom land, a pard and I saw a small bird of some kind land on the back of a bald eagle and ride it for several wing beats. The bird was harassing the eagle. It was slightly smaller than a sparrow, like a wren of some kind maybe, darting and pecking at the big bird as it flapped along slowly 40 feet above us. Twice the little bird zoomed onto the eagle’s back between its wings, pecked and then held on with its beak and rode the eagle. We were looking up into a fairly bright overcast sky and my eyes could not pick up color details on the small bird. It just looked dark against the clouds.