According to Mitch Cleary on AFL Trade Radio, the Hawks offered Birchall just a rookie contract, with the 31-year-old opting to go and reunite with Chris Fagan at the Lions.
Birchall spoke to the Lions’ website on Thursday, saying how excited he is to join.
“It happened reasonably quickly,” he said.
“I’m excited to start something a bit different and get up there.
“[Chris Fagan] has done some really good things at the Lions over the last few years and they were really good to watch in 2019.
“I’m looking forward to playing under him and hopefully helping the guys go the next step in 2020.”