This pose is Tittibhasana A. It's in the Ashtanga Intermediate series (Nadi Shodhana). Each yoga asana has an ancient story behind it.
Tittibha = a little bird living along the sea. A story of the tittibha birds can be used as a symbol of yoga, where the birds lay their eggs, live peacefully, and the sea swallows them up; but, the sea gives them back when commanded to do so.
The sea with its might and power represents the power of illusion, ignorance and prejudice (i.e., citta - all aspect of human existence subject to change).
The small tittibha bird stands for the effort of the yogi, an effort which seems ineffectual when compared with the challenge.
But just as the little tittibha bird succeeds, the yogi can calm citta through practice and shatter illusion. (Story from the Panchatantra).