A question prompted by the campaign for a new UK national bird. Does your setting have a national bird?
Indeed, does it have any birds or other small animals besides the norm... and monsters?
PCs venturing into the sewers have a good chance of facing giant rats, but if they go on rooftops they tend not to face giant sparrows or pigeons. One is a classic, the other suggests a comedic parody. Is cuteness a factor? People tend not to take scraps of meat to feed the rats in the park...
Speaking of parks, I saw a pied wagtail recently - the size of a sparrow but much less common around here and strikingly odd due to its black and white plumage. A small detail I might sneak into a fantasy setting - all the birds are unfamiliar.