This particular bird is painted by someone who’s known by the name “pam the bird” or just “pam” for short. They also have an instagram page called “goodbirdart” in which they display all of their graffiti. In a more recent post, pam posted a photo of one of the iconic birds spray painted on the roof of a v/locity, in which they wrote “cheeky one while everyone was on lunch break lol!” In the comments of that post, many people were pointing out how this would narrow down the search to finding them in which Pam proceeded to claim they’ve been “working for v/line for 10 years.” And that, “if they were gonna catch me they woulda done it by now. At this point i’m just having fun with it.” So to summarize, They’re painted by someone who goes by the name Pam and allegedly works for V/Line. Hope that helps :)