Whenever a Bird is put into your graveyard from the battlefield, put a feather counter on Soulcatchers' Aerie. Bird creatures get +1/+1 for each feather counter on Soulcatchers' Aerie.
Near Mint - $0.50
Lightly Played - $0.47
Moderately Played - $0.40
Heavily Played - $0.30
Damaged - $0.25
Near Mint Non-English - $0.50
Lightly Played Non-English - $0.47
Moderately Played Non-English - $0.40
Heavily Played Non-English - $0.30
Damaged Non-English - $0.25