"Isn't there a counting-down song with a mother duck mourning the loss of all her offspring in the next-to-last verse, then finding them all in the last verse?"

Ugh, yes.

Five little ducks went out to play
Over the hills and far away
Mama duck said "Come back quack quack"
But only four little ducks came back

(And so on until the last duck is gone)

Now SAAAAD Mama duck said "quack quack quack quack"....
And all the little ducks came running back!

The tune is very similar to that OTHER duck song

Five little ducks that I once knew
Short ones, fat ones, a yellow one too
But the one little duck with a feather on his back
He led the others with a Quack, quack, quack!

I've had to sing those songs so very much these past few years. I love my nieces, truly I do, but I'm So Tired Of Those Songs!