tāsām - of the little birds; patatraiḥ - by the wings; su-sparśaiḥ - gentle to the touch; kūjitaiḥ - their chirping; mugdha - attractive; ceṣṭitaiḥ - by the activities; pratyudgamaiḥ - by their efforts to fly by eagerly jumping up; adīnānām - of the happy (children); pitarau - the parents; mudam āpatuḥ - became joyful.

The parent birds became very joyful by observing the soft wings of their children, their chirping, their lovely innocent movements around the nest and their attempts to jump up and fly. Seeing their children happy, the parents were also happy.