Phyllis Gottlieb, in a poem full of the sensibility of children at play and the social reflections found in childhood rhymes, presents the reader with a thoughtful aside:
(as I was sitting beneath a tree
a birdie sent his love to me
and as I wiped it from my eye
I thought: thank goodness cows can't fly)
Size matters. From "Ordinary Moving" in the collection of the same title.