Where to Find and Catch Shelgon
From Pokemon Go Wiki
Shelgon are found and captured in Nest and Habitat locations.
Nests
Shelgon Nests are locations that consistently spawn Shelgon.
Habitats
Shelgon Habitats are spawn locations where Shelgon is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here:
