What is the adverb form of migration?

There isn't a single, commonly used adverb form of "migration." However, depending on the context, you could use a few different adverbs to describe the act of migrating:

* Migratorily: This is a formal and somewhat uncommon option. It directly relates to the noun "migration" and can be used to describe something happening in the way that migration does.

* Migratingly: Similar to "migratorily," this is a less common option and means "in a migrating manner."

* Migratory: While this is an adjective, it can sometimes be used as an adverb, particularly in phrases like "they moved migratory."

Instead of using an adverb, you could also use phrases like:

* In a migratory manner

* Through migration

* By migrating

The best choice will depend on the specific context of your writing.