The rails migrate en masse from Madagascar when there's too many of them, and all of them will die except the ones that fly east and find a couple small islands. If they're lucky, they land there and thrive. On one island, they don't have predators and so they eventually lose the ability to fly. Over thousands of years, the island got submerged and they all drowned. Then, thousands of years later, the island resurfaced and another migration happened and the next batch of rails found it, moved in, and slowly lost the ability to fly.
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https://www.cnn.com/2019/05/10/africa/white-throated-rail-extinction-scli-intl-scn/index.html
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Edit: spelling and grammar because I shouldn't try to comment at 4am with one eye open.
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https://www.cnn.com/2019/05/10/africa/white-throated-rail-extinction-scli-intl-scn/index.html
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Edit: spelling and grammar because I shouldn't try to comment at 4am with one eye open.