Bird (groin) was sent to Triple-A Albuquerque on Tuesday to begin a rehab assignment.
Bird has been out since late June with a groin strain, but he resumed throwing a few days ago and is now ready to test things out in a game setting. The reliever shouldn't need many rehab appearances since he hasn't missed much time, but with the All-Star break looming the Rockies could choose to hold him out until the second half.