A 추임새 is not a bird; it is an exclamation shouted by the drummer (북잡이) in a 판소리 to stir up excitement in the audience. When the singer of the 판소리 pauses at the end of a stanza, the drummer might say something such as, 좋다, 좋지, 그렇지, 잘한다, 얼씨구, 허이, 아먼, 어디, 으이, or 흥 to encourage the singer and to stir up excitement in the audience.
I mention this because I read here that "짠짜라," which is a song that I discussed here, was once a kind of 추임새, shouted by members of the brass section of a band during certain segments of the band's performance. The same article says 짠짜라 is used today to refer to the kind of music once played by itinerant bands that used to travel around Korea about a hundred years ago.
Also, I noticed the word 불량 감자 in the 짠짜라 music video. It was written on the sign hanging on the neck of the man who got on the bus with a box of potatoes. I am still trying to pin down the exact slang meaning of the word, but the original meaning of 불량감자 is "potatoes damaged during harvert" or "potatoes where the eyes have been allowed to sprout."
At first, I thought 불량감자 was just an indirect way to refer to a 불량자, which is "a rascal," "a rowdy," "a scoundrel," or "a punk," but it does not seem to be used that way in some writings I have seen on the Internet. I will continue to look for the slang meaning of the word, but if anyone knows it already, I would appreciate if you would let me know by posting it to the comments section of this post.