How to filter cards
Open Anki (preferably on desktop) and go to the browser
In the left section, scroll until “Tags” and find the country you want to study under “UB”
Search for all cards in the deck NOT having this tag (- means not)
Select all cards (Ctrl+A), then right click and toggle suspend
Now when you close the browser and start studying the deck, only birds that appear in the country will appear.