Birds

 A younger gopī told her mother, "My dear mother, the birds, who are all looking at Kṛṣṇa playing on His flute, are sitting very attentively on the branches and twigs of different trees. From their features  they have forgotten everything and are engaged only in hearing Kṛṣṇa's flute. This proves that they are not ordinary birds; they are great sages and devotees, and just to hear Kṛṣṇa's flute they have appeared in Vṛndāvana forest as birds.

KRSNA, The Supreme Personality > Volume 1 > KB 1-21 / The Gopis Attracted