Treasure Island

Al Jouri wanted to closely know the Flamingo birds that lands in Qatar during their migration. Her grandpa suggested a family trip to the full of mangroves; Bin Ghannam Island. But why did Al Jouri suggest calling it: The Treasure Island? And what is the link between it, the lost maps, and the Center of Rare Manuscripts?
Can the answer be found in the bottle floating on the island’s water surface?