A float-equipped DHC-3T Turbine Otter airplane, N104BM, struck an eagle while en route at about 2,500 feet and 10 miles northeast of the Homer-Beluga Lake Seaplane Base, Alaska. The two airline pilots sustained no injuries, and the airplane sustained substantial damage. The airplane was flying straight and level, at about 120 miles per hour (mph), at an altitude of about 2,500 feet, and heading northeast at the time of impact with the eagle. The flight crew notified the Homer Flight Service Station of the bird strike and their intentions to return to base. At this time, the airplane was flying normal with no control issues. However, the first attempt at landing was aborted due to an uncontrollable aileron roll to the left when the airspeed decayed below 75 mph. The flight crew declared an emergency and requested emergency services. During the subsequent landing, the flight crew maintained the airspeed above 75 mph until an altitude that was just above the surface of the water. The landing was accomplished without any further control issues. PROBABLE CAUSE: “An in-flight collision with a bald eagle, which resulted in substantial damage to the left wing.”