The 24-year-old, 139-game rebounding backman was third in the Hawks' best and fairest count last season and an All Australian nominee.
After committing until the end of 2015, Birchall said he was aiming for another flag and to take on a leadership role.
"I'm not sure about captaining the club but definitely being a leader, particularly down the backline leading those guys," Birchall told the Hawks' website.
"Just being part of the leadership group, I could see myself doing that in coming years."
Birchall said he had been disappointed in his 2009 and 2010 seasons, but pleased with the way he bounced back last year and so far this season.