After a while after completing more errands for the Railroad, Drummer Boy will inform you that Carrington is looking for you. Talk to Carrington to receive this quest. In this quest, you have to find one of their agents, Blackbird, thought to have died when Safehouse Augusta fell. Like before, head to the dead drop location to get more details about your quest.
Head to the Shamrock Taphouse which is marked in your map after retrieving the Blackbird Report. Fight your way through the raiders and find Blackbird’s body. Loot the note from his body to update this quest. Report back to Carrington to complete the quest.