biri is the largest and northernmost of the balicuatro islands and is about long northwest and southeast and wide. it is generally high with a rocky perpendicular bluff on its northwestern side. its coastline is covered with mangroves and has gravel beaches on its western side. it is surrounded by macarite, cagnipa, talisay, magesang and other smaller unnamed islands and is protected by fringing reefs. in 2000, the island municipality had a population of 8,700 distributed in 8 barangays.