Alpha Pokémon are always present in fixed locations, but their levels vary. Shinies are extremely rare. Your best bet for finding Shinies is during Mass Outbreaks and Massive Mass Outbreaks, where the odds are significantly increased. Listen for the distinct sparkling sound and visual cue. Completing a Pokémon's Pokédex entry to Research Level 10 and achieving a Perfect Pokédex entry further boosts Shiny odds for that species.
