Ayala, 35, went 5-5 with a 2.64 ERA and a 49.0 ground-ball percentage in 75 innings for the O's last year. He has allowed two runs in two innings across two appearances so far in 2013. Ayala is owed $1 million this year and will become a free agent after the season.
Atlanta lost lefty reliever Jonny Venters for about a month due to elbow problems, so the move gives them some added bullpen depth. Ayala figures to join righty Jordan Walden and lefty Eric O'Flaherty as part of manager Fredi Gonzalez's setup crew in front of closer Craig Kimbrel.
Jones, 24, was traded from the Indians to the Braves for Derek Lowe before last season. He went 2-5 with a 3.90 ERA and 9.2 K/9 in 60 relief innings for Atlanta's Double-A affiliate last year. The Orioles will assign him to their Double-A affiliate.
Baltimore had been carrying eight relievers, so trading Ayala gets them back down to a normal 12-man pitching staff. Outfielder Chris Dickerson has been recalled to take the roster spot.