Wow
even though I am french the meaning remains pretty unclear... and word associations sound weird...
anyway here is a litteral translation, to be improved and re-thought by some other people who may have some better idea thereafter
Si je suis...d'une autre etoffe
La trame n'en est pas de vos oiseaux de mer
Mais de leur froides proies ourdie.
If I am... (made) of another tissue
its weft is not of your seabirds
but of their cold warp prey