In bird pose (eagle, crow, rooster, peakcock), common factors are flexion of the thoracic spine, abduction of the scapulae, and extension of the cervical spine. In other words, wings are spread and the beak is lifted.

These actions require precision and strength in the muscles of the spine to achieve cervical extension without engaging the trapezius, which will interfere with the action of the scapulae and arms.