One day, there was great commotion outside the Elders cell: two swallows had started a fierce fight with each other! The Elder was troubled. He went outside and beheld a distressing spectacle: the stronger swallow was attacking the other with its beak and literally plucking out its feathers. Without wasting any time, he chased the stronger swallow away. He lovingly took the injured bird in his hands and rescued it; as a result of his nursing, it survived.
Thereafter, just as the lion of St. Gerasimos used to follow the Saint everywhere, showing its gratitude and dedication, so also did this swallow: it flew in front of the Elder, fluttered its wings, frolicked, and sang.
One day, the Elder went outside, either to marvel at God in His works or to pray in silence. The swallow, his faithful friend and companion, was happily flying beside him.
The Elder sat down in the fruit-drying room a short distance from the monastery, and fell asleep without realizing it; but the swallow suddenly began to flutter rapidly above his head, chirping loudly, as if it wanted to wake him up and warn him of some danger.
And in very truth, when the Elder awoke, what did he see? A large reptile not too far away from him. His companion had in turn performed its own act of charity for the merciful.
Source | Archimandrite Ioannikios, Philaret of Kostamonitou, in Sygchrones Hagioreitikes Morphes—9 [Contemporary Athonite Personalities: Vol. IX] (Oropos: Holy Monastery of the Paraclete, 1983), pages 80-81.