釋氏要覽 1.139

1.139

西域記云。昔有比丘見群雁飛翔。戲言知時。忽有一雁投下自殞。眾曰此雁垂誡。宜旌厚德。於是瘞雁建塔。

The Records of the Western Regions says: Formerly, a monk saw a flock of wild geese flying and playfully remarked that they knew the season. Suddenly, one goose plummeted down and killed itself. The assembly said: 'This goose offers a warning; we should honor its profound virtue.' Thereupon they buried the goose and built a stūpa.