Minecraft 1.9 mushroom island seed by mountains
This is one of the more uncommon Minecraft 1.9 mushroom island seeds. Players actually start off on a small patch of grass on the edge of the mushroom island biome. It's pretty much impossible to actually spawn in or on a mushroom island, to start off anywhere nearby requires a different biome up against the mushroom island.
The seed is: 7670100323430838974
Another funny part about this 1.9 Minecraft mushroom island seed is that it's not actually an island. This is connected to a really cool mountain environment. Other than that it's a pretty normal mushroom biome. These environments are the only places to find mushroom cows and it's a really cool place to make giant mushroom farms.