Howlett, 29, played 124 games for the club, and was one of the Bombers who returned from suspension in 2017.
The hard-working half-forward/midfielder spent seven years at Essendon after being selected at pick 30 in the 2010 Rookie Draft.
Bomber’s coach John Worsfold spoke glowingly about the positive impact Howlett had on the club during his career.
“Ben is an unbelievably strong character in terms of his leadership and team values,” Worsfold told essendonfc.com.au.
“He is always focused on wanting to play his role for the team, to the best of his ability.
“There’s no doubt 2016 was tough on the players who had to watch from the sidelines, but the way Ben returned, performed and mentored his younger teammates is a credit to him and his family.
“The modern game is relentless and to start as a rookie and go onto play more than 100 games is an outstanding effort, and Ben leaves having made a huge contribution to the Essendon Football Club.
“Ben will always be welcome at Essendon, and on behalf of everyone at the Club we wish him and his young family all the very best for the future.”
Bird, 28, who was recruited from the Sydney Swans in the 2015 trade period, played 20 games for the Bombers.
Bird was drafted at pick 59 in the 2007 national draft, playing 137 games for the Swans, including the 2012 premiership.
Worsfold also thanked Bird for his contribution to the football club.
“Craig has been a pleasure to work with during his career at Essendon,” Worsfold said.
“His attitude, leadership and commitment to the success of the Club has been outstanding.
“Craig played a key role in 2016 through our midfield and helped us through a very tough year.
“On behalf of the Club, I would like to thank Craig and wish him all the best with his future endeavours.”