"...Four Colly Birds..."
I actually had to look this up on Wikipedia. I grew up in the South of England in the 1970s, and we sang "four colly birds", and then at some point I realised it should be "four calling birds" and thought I'd been singing it wrong. Then I saw this sentiment. It clearly says "four colly birds". I've looked it up. It really should be "Four Colly Birds". Colly is an old word for black, so this song is really about four blackbirds! You learn something new every day :-)
"...Three French Hens..."
"...Two Turtle Doves..."
"...and a Partridge in a Pear Tree!"
Oh yes, obsession, that's what I'm talking about ;-)