The Fourth day of Christmas my true love gave to me:

Four calling birds, three French hens, two turtle doves, and a partridge in a pear tree

The song originallally wasn't about calling birds. There is no such thing. However there is a collie bird in England. Collie  refers to the mining industry and the color black. So I got four blackbirds for the fourth day. I didn't get four collie dogs -  there's another bit of trivia I need to explore. 4. FOUR CALLING BIRDS