On May 16, 2002, about 1230 Alaska daylight time, a Robinson R-44 helicopter, N344AK, sustained substantial damage while maneuvering near trees, about 23 miles southwest of Cantwell, Alaska. The helicopter was being operated as a visual flight rules (VFR) public use government flight when the accident occurred. The helicopter is registered to Quicksilver Air Inc., Fairbanks, Alaska, and was operated under contract by the U.S. Geological Survey, Anchorage, Alaska. The commercial certificated pilot, and the two passengers, were not injured. Visual meteorological conditions prevailed. A VFR flight plan was filed. The flight originated at the McKinley National Park airport, Denali National Park, Alaska, about 1130. The U.S. Department of Interior, Office of Aircraft Services, Boise, Idaho, notified the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on May 16, that the helicopter was being utilized by the U.S. Geological Survey to track caribou. The area of the accident was in the Denali National Park boundary. During a telephone conversation with the NTSB IIC on May 16, the pilot reported that he was maneuvering the helicopter in an attempt to move radio-collared caribou out of an area of trees along the west fork of the Chulitna River. Prior to beginning the maneuvering, the pilot said he conducted an out-of-ground-effect hover power check, and was satisfied with the helicopter's available power. He then began an out-of-ground-effect hover near several caribou. The pilot said that when he raised the collective control to move from his hover position, the low rotor annunciator sounded. He said he did not have sufficient power available to climb away from his position, and the helicopter began to settle toward the ground. One of the helicopter landing gear skids settled into low bushes, and the pilot was able to regain sufficient rotor RPM to move to a nearby landing area. After landing, the pilot found that one of the main rotor blades had a tear in the bottom surface of the blade surface. The other main rotor blade had several dents. The pilot determined the helicopter was not flyable. He said he did not feel any rotor contact with the trees. The pilot described the weather conditions as clear, wind from the southeast about 10 knots, and the temperature was 52 degrees F.