Of Barnacles, Which Grow from Fir Timber, and Their Nature

There are likewise here many birds called barnacles, which nature produces in a wonderful manner out of her ordinary course. They resemble the marsh geese, but are smaller. Being at first gummy excrescences from pine beams floating on the waters, and then enclosed in shells to secure their free growth, they hang by their beaks like seaweeds attached to the timber. Being in process of time well covered with feathers, they either fall into the water or take their flight in the free air, their nourishment and growth being supplied, while they are bred in this very unaccountable and curious manner, from the juices of the wood in the sea-water. I have often seen with my own eyes more than a thousand minute embryos of birds of this species on the seashore, hanging from one piece of timber, covered with shells, and already formed. No eggs are laid by these birds after copulation, as is the case with birds in general; the hen never sits on eggs in order to hatch them; in no corner of the world are they seen either to pair, or build nests. Hence, in some parts of Ireland, bishops and men of religion make no scruple of eating these birds on fasting days, as not being flesh, because they are not born of flesh. But these men are curiously drawn into error. For, if any one had eaten part of the thigh of our first parent, which was really flesh, although not born of flesh, I should think him not guiltless of having eaten flesh. Repent, O unhappy Jew, recollect, though late, that man was first generated from clay without being procreated by male and female; nor will your veneration for the law allow you to deny that.

 - Giraldus Cambrensis, The Topography of Ireland. 1187.