Bald Eagles - first trial of the season

Bald Eagle
Nikon D300s, Sigma 50-500mm / f4.5-6.3 APO DG HSM

What's wrong with this picture? It shows all the symptoms of a heavily cropped image, lacks detail and sharpness. Period! Great light this afternoon, temperatures were not too cold, with other words excellent conditions to go out shooting Bald Eagles. To make a long story short, I left home too late this afternoon for going down the river to dam #14. I wasted time by stopping at dam #11 in Dubuque. No eagles there, except for one high up in the trees. I arrived at dam #12 in Bellevue, Iowa around 3PM. The dilemma at this dam is that a high wire fence obstructs the view to the area below the dam, where the Bald Eagles usually hunt for fish. Another photographer, Tracy form Chicago, invited me to join her on top of a picnic table near the fence, that obviously other frustrated photographers had already moved there. This was a very nice gesture of her and I enjoyed the conversation about nature photography while we were both shooting burst after burst in order to capture a good image of the eagles. Worked out  well for bypassing the fence but during the next hour (still wonderful light!) none of the eagles came even close to really fill the frame. There were a couple fishing boats below the dam on our side of the Mississippi River and I wonder, if this made the eagles prefer the opposite side. Even if I wasn't really pleased about my results today, it was good practice to handhold the heavy lens and not much beats being outside on a perfect winter day anyway...