Those aren't powers...I think Sasuke had hawk and snake summonings since his training days with Orochimaru.
It makes sense because since shippuden Kishi never showed Sauce training much. Sasuke lost his white snake powers against Itachi but still managed to summon snakes in the war arc.
Against Danzo Tobi had no idea Sasuke had hawk summonings despite having a white zetsu follow him around, which means he learned it during the time skip with Oro.
You just sign a contract with that animal in blood as naruto and Jariaya did with the toad. Then u can summon them in proportion to your chakra.
But since u cant have a contract with 2 animals, maybe hawks just got a thing for him lol... Unless its genjutsu