“The example of two birds in the same tree is given to illustrate the presence within the heart of the material body of both the individual soul and the Supersoul, the Personality of Godhead. Just as a bird makes a nest in a tree, the living entity sits within the heart. The example is appropriate because the bird is always distinct from the tree. Similarly, both the individual soul and the Supersoul are distinct entities, separate from the temporary material body. The word balena indicates that the Supreme Personality of Godhead is satisfied by His own internal potency, which consists of eternality, omniscience and bliss. As indicated by the word bhūyān, or “having superior existence,” the Supreme Lord is always in a superior position, whereas the living entity is sometimes in illusion and sometimes enlightened. The word balena indicates that the Lord is never in darkness or ignorance, but is always full in His perfect, blissful consciousness.
Thus, the Lord is niranna, or uninterested in the bitter fruits of material activities, whereas the ordinary conditioned soul busily consumes such bitter fruits, thinking them to be sweet. Ultimately, the fruit of all material endeavor is death, but the living entity foolishly thinks material things will bring him pleasure. The word sakhāyau, or “two friends,” is also significant. Our real friend is Lord Kṛṣṇa, who is situated within our heart. Only He knows our actual needs, and only He can give us real happiness.
Lord Kṛṣṇa is so kind that He patiently sits in the heart, trying to guide the conditioned soul back home, back to Godhead. Certainly no material friend would remain with his foolish companion for millions of years, especially if his companion were to ignore him or even curse him. But Lord Kṛṣṇa is such a faithful, loving friend that He accompanies even the most demoniac living entity and is also in the heart of the insect, pig and dog. That is because Lord Kṛṣṇa is supremely Kṛṣṇa conscious and sees every living entity as part and parcel of Himself. Every living being should give up the bitter fruits of the tree of material existence. One should turn one’s face to the Lord within the heart and revive one’s eternal loving relationship with one’s real friend, Lord Kṛṣṇa. The word sadṛśau, or “of similar nature,” indicates that both the living entity and the Personality of Godhead are conscious entities. As part and parcel of the Lord we share the Lord’s nature, but in infinitesimal quantity. Thus the Lord and the living entity are sadṛśau. A similar statement is found in the Śvetāśvatara Upaniṣad (4.6):
dvā suparṇā sayujā sakhāyā samānaṁ vṛkṣaṁ pariṣasvajāte
tayor anyaḥ pippalaṁ svādu atty anaśnann anyo ’bhicākaśīti
“There are two birds in one tree. One of them is eating the fruits of the tree, while the other is witnessing the actions. The witness is the Lord, and the fruit-eater is the living entity.”
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Eleventh Canto, Chapter 11 – Text 06.