The single-engine helicopter encountered a settling with power condition resulting in a hard landing on a marsh. The 3,300-hour commercial pilot was hovering the helicopter at approximately 100 feet above the ground (AGL) while performing a wildlife/mapping survey, approximately 100 feet above ground level (AGL), when he lost control of the helicopter. The helicopter's tail-boom separated and the main rotor blades impacted the ground during the hard landing. The helicopter came to rest in the upright position with the nose pointing skyward. The pilot was able to exit the helicopter unassisted. The pilot reported that he had a 15 knot tailwind, when he slowed the helicopter to mark a waypoint. As he applied left torque pedal and added collective, the main rotor RPM drooped. The pilot was unable to recover sufficient rotor RPM to prevent ground contact. The pilot further stated that there were no malfunctions with the helicopter's reciprocating engine or controls. Visual metrological conditions prevailed at the time of the accident and the temperature was reported as 85-degrees Fahrenheit.