Oh, wait--found it online. Sort of. Everybody has the "jaybird" verse posted as "tapir", which is a pretty hilarious mondegreen, really.

I never said it made sense, anyway.

"MUSKRAT" a la the Everly Brothers

Muskrat, muskrat, what makes your back so slick?
I've been livin' in the water all my life,
It's a wonder I ain't sick,
I ain't sick, I ain't sick, I ain't sick,

Groundhog, groundhog, what makes your back so round?
I've been livin' in the ground all my life,
There's no wonder I ain't drowned, [?]
I ain't drowned, I ain't drowned, I ain't drowned.

Jaybird, jaybird, what makes you fly so high?
I've been eatin' these acorns all my life,
It's a wonder I don't die,
I don't die, I don't die, I don't die.

(instrumental)

Rooster, rooster, what makes your beak so hard?
I've been scratchin' in the barnyard all my life,
It's a wonder I ain't tired,    [said "tahrd", of course]
I ain't tired, I ain't tired, I ain't tired.

Bobcat, bobcat, what makes your tail so long?
I've been prowlin' around all my life,
It's a wonder I ain't gone,
I ain't gone, I ain't gone, I ain't gone.