[The birds] in the Byzantine scheme would have been as abstract and typical as the birds of an Egyptian hieroglyphic. The birds of the later realistic epoch, when the painters of the nineteenth century had brought to the last perfection, or the last satiety, the studies of optics or of physics begun in the sixteenth, might well have been a most detailed and even bewildering display of ornithology. But the birds to whom St. Francis preached, in the vision of the thirteenth-century art, were already birds that could fly or sing, but not yet birds that could be shot or stuffed; they had ceased to be merely heraldic without becoming merely scientific. And as, in all studies of St. Francis, we always return to that great comparison which he at once denied with all his humility and desired with all his heart, we may say that they were not wholly unlike those strange birds in the legend, which the Holy Child pinched into shape out of scraps of clay, and then started into life and swiftness with a clap of his little hands.
– “Giotto and St. Francis”, in On Lying in Bed.
[original source unknown (to The Hebdomadarian)]