Perry's Index to the Aesopica
Fables exist in many versions; here is one version in English:
THE RAVEN AND THE SWAN
A story about a raven, exhorting us to do what is natural
The raven saw the swan and envied his white colour. Thinking that his own colour
was due to the water in which he bathed, the raven abandoned the altars where
he found his food and instead joined the swans in the swamps and the rivers.
This did nothing at all to change the raven's colour, but he starved to death
from a lack of food.
A change of habit cannot alter a person's nature.
Aesop's Fables. A new translation by Laura
Oxford University Press (World's Classics): Oxford, 2002.
cover, with new ISBN, published in 2008; contents of book unchanged.
Perry 398: Gibbs (Oxford) 335 [English]
Perry 398: L'Estrange 161 [English]
Perry 398: Townsend 36 [English]
Perry 398: Aphthonius 40 [Greek]
You can find a compilation of Perry's index to the Aesopica in the gigantic appendix to his
edition of Babrius and Phaedrus for the Loeb Classical Library
(Harvard University Press: Cambridge, 1965). This book is an absolute must for anyone interested
in the Aesopic fable tradition. Invaluable.