They have built rock walls on the islands to prevent all of the guano from sliding into the sea. Once every 7 years they come out to harvest it. It takes a lot of manpower as they put the guano in the round concrete bins as they collect it then they bag it and lower it from the structure built on the side of the island into waiting boats. They live on the islands for 2 to 3 months while harvesting. The last harvest was in 2011 and you can sure tell…when you get between the islands plug your nose!