Minecraft wiki entry for Spawn, associated text: Plains
At main plains biome
Small islands in an ocean (islands are usually a plains biome)
Patch of plains next to desert, badlands, or snowy plains
Forest
At main forest biome
Small islands in an ocean (islands can also be a forest biome)
Dark Forest
Taiga
At main taiga biome
Patch of taiga next to old growth pine taiga
Near beach, snowy taiga, or windswept hills
Jungle
Savanna (only regular variants)