Pokémon GO Rufflet was featured in an event promoting Pokémon the Movie: Secrets of the Jungle. It appeared in Raids and from Eggs, but players have had difficulty finding Rufflet. If you missed out on the event, here's where else you can still catch a Rufflet in Pokémon GO.
Pokémon GO Rufflet: Where to Catch
Rufflet is a somewhat rare Flying and Normal-type Pokémon. Even during the event, Rufflet was very difficult to find despite being featured. It was so rare, the Pokémon GO data analysis site The Silph Rd could not verify Shiny Rates due to low encounters. Since it's a Flying-type, you might have better luck finding one in urban locations.
Rufflet was only in Raids for the movie event, so it has since left the Raid rotation. You won't have any luck finding it here anymore.
Shiny Rufflet is also available in the wild, but with the already scarce nature of Rufflet you'll have a bit of trouble finding one. Shiny Pokémon only appear once every 450 encounters and don't appear Shiny on the map. You'll want to catch as many Rufflet as you can anyway if you want to evolve them into Braviary, so don't miss out on any you see.