No Limit

A wonderful bird is the Pelican.
His beak can hold more than his belly can.
He can hold in his beak
Enough food for a week!
But I'll be darned if I know how the hellican?

And another version:

A wonderful bird is the pelican,
His bill can hold more than his beli-can.
He can take in his beak
Food enough for a week
But I’m damned if I see how the heli-can.

Some say, this limerick is by Edward Lear, "the undisputed master of the limerick", 1812-1882.
Others see Poet Ogden Nash as its author. (died 1971)
The verse has also been attributed to Dixon Lanier Merritt, a humorist (died in 1972).