In ancient times there was an immortal who cultivated in the remote mountains. He sat constantly under a giant tree and cultivated Chan, concentrating his mind to get rid of all his false thinking.
One time during the winter, when the weather was extremely cold, at about sunset, a hungry, freezing little bird flew up to the immortal and nestled up against his chest, attempting to absorb some warmth from the immortal's body in order to prolong its own life. The immortal continued to sit in full lotus, not daring to move his body the slightest bit, for fear he might disturb or frighten the little bird. His only concern was that the bird could rest comfortably.
Not until the next day, after the bird flew off to find another place to nest, did the immortal allow himself to move and come out of samadhi.
From this account we can know something of the magnitude of the ancients' kindness and compassion even toward little birds. This is something we should study and develop within ourselves.