Where to Find and Catch Vullaby
From Pokemon Go Wiki
Vullaby are found and captured in Nest and Habitat locations.
Nests
Vullaby Nests are locations that consistently spawn Vullaby.
Habitats
Vullaby Habitats are spawn locations where Vullaby 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: