Island

Spawning data tags simply contain a list of Biomes. If you're referring to this list for a Pokemon, please double-check if it has an Anti Condition or Anti Biome. Anti Conditions and Anti Biomes are a way to essentially state: not in this biome/condition, so you'll need to cross-reference them. For instance, if a Pokemon is set to spawn in is_ocean, but has an anti condition of is_cold, it will not spawn in cold oceans.

Our Pokemon spawns are generally based on default Cobblemon configurations with additions to allow the entire dex to spawn in all Minecraft biomes and supported biome mods. Most biome mods are supported such as Terralith, Oh Biomes You'll Go, Incendium, Better Nether, Gardens of the Dead, and The Bumblezone. Other biome mods may also be compatible, provided they label their biomes with data tags.

Island Biomes
minecraft:mushroom_fields	terralith:alpha_islands	terralith:alpha_islands_winter
terralith:mirage_isles	terralith:warped_mesa	byg:lush_stacks
wythers:cold_island	wythers:desert_island	wythers:frigid_island
wythers:frozen_island	wythers:jungle_island	wythers:mediterranean_island
wythers:mediterranean_island_thermal_springs	wythers:mushroom_island	wythers:temperate_island
wythers:tropical_island	wythers:tropical_beach	wythers:tropical_volcano