The pilot reported he was attempting to take off from an off-airport site on a remote island. The takeoff area was surrounded by trees and brush, and the pilot said there was a right, quartering headwind from the northwest which he estimated as 10 to 15 knots, with higher gusts. Shortly after lift-off, the pilot said he lost control of the airplane and collided with adjoining brush. He said he was unaware if the wind suddenly quit, or if he was blown into the brush by a wind gust.