Mbh 2.40.2

“There lived of yore an old swan on the sea-coast. Ever speaking of morality, but otherwise in his conduct, he used to instruct the feathery tribe. Practise ye virtue and forego sin,--these were the words that other truthful birds, O Bhishma, constantly heard him utter And the other oviparous creatures ranging the sea, it hath been heard by us, O Bhishma use for virtue’s sake to bring him food. And, O Bhishma, all those other birds, keeping their eggs, with him, ranged and dived in the waters of the sea. And the sinful old swan, attentive to his own pursuits, used to eat up the eggs of all those birds that foolishly trusted in him. After a while when the eggs were decreasing in number, a bird of great wisdom had his suspicions roused and he even witnessed (the affair) one day. And having witnessed the sinful act of the old swan, that bird in great sorrow spoke unto all the other birds. Then, O thou best of the Kurus, all those birds witnessing with their own eyes the act of the old swan, approached that wretch of false conduct and slew him.