User blog comment:Logo8th/What is the Bird Behind the Graphorns?/@comment-4625990-20160930101739/@comment-4625990-20160930114829

Well seen, I found another article which confuses "Fwooper" and "Swooper", and which says "Swooper song will eventually drive the listener to insanity and the Swooper is consequently sold with a Silencing Charm upon it". You're right, it's apparently indeed a Fwooper.