The pilot reported that he was performing a maintenance test flight at an airport located right on the water's edge, on an island in the middle of the Pacific Ocean. The pilot stated that as he began the landing flare, several birds flew in front of his windscreen. To avoid hitting the birds, the pilot maneuvered the airplane to the left. The airplane subsequently landed hard on the left main landing gear, just left of the runway centerline. The pilot reported that after touchdown, to avoid running off the runway, he applied right braking action, which resulted in the airplane turning violently to the right and coming to a stop with the nose between 20-30 degrees from runway centerline. Postaccident inspection of the airplane found that the left wing was wrinkled and structurally damaged.