Verse 2.9.4

अथ यत्संगववेलायां स आदिस्तदस्य वयांस्यन्वायत्तानि तस्मात्तान्यन्तरिक्षेऽनारम्बणान्यादायात्मानं परिपतन्त्यादिभाजीनि ह्येतस्य साम्नः ॥ २.९.४ ॥

atha yatsaṃgavavelāyāṃ sa ādistadasya vayāṃsyanvāyattāni tasmāttānyantarikṣe'nārambaṇānyādāyātmānaṃ paripatantyādibhājīni hyetasya sāmnaḥ || 2.9.4 ||

4. Next, when the sun-rays spread all over a short while after sunrise, that form of the sun is the ādi of the Sāma. This form is connected with the birds. They somehow or other feel they have a safe shelter then, and that is why they are able to fly freely about in the sky without any support. They also behave as if they are joining in the ādi offered to the Sāma.

Word-for-word explanation:

Atha, next; yat, that; saṅgavavelāyām, in the morning [i.e., after sunrise, when the sunlight has spread far and wide]; saḥ ādiḥ, that is the ādi [of the Sāma worship]; vayāṃsi, birds; tat asya, that form of the sun [at that time]; anvāyattāni, makes them feel secure; tasmāt, this is why; tāni, they [the birds]; anārambaṇāni, without any support; ātmānam, their own bodies; ādāya,

Commentary:

The sight of the sun after sunrise fascinates the birds. The form of the sun at this time is the ādi (or Om) of the Sāma, and the birds feel they are a part of this ādi. They feel secure. Though they have no support, they are able to fly about in the sky freely. It is as if they are joining in the ādi hymn offered to the Sāma.

As the birds fly, they depend on their own ‘self’ (ātman). Because the words ātman and ādi have the common ā, the birds feel drawn towards the ādi.