Dove migrated north to county (5)
I believe the answer is:
devon
'to county' is the definition.
(I've seen this before)
'dove migrated north' is the wordplay.
'migrated' indicates an anagram (I've seen 'migrate' mean this).
'north' becomes 'N' (abbreviation).
'dove' with letters rearranged gives 'devo'.
'devo'+'n'='DEVON'
(Other definitions for devon that I've seen before include "County in southwestern England" , "West country county" , "Clotted-cream county" , "English county" , "Ilfracombe's county" .)