A man who steals the lead off of a house or church. “Bluey” is slang for lead, so called from its colour. To “pigeon” is to gull, cheat, or fub. Hence, blue-pigeon, one who cheats another of his lead, or fubs his lead. “Flyer,” of course, is one who flies off with the stolen lead.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894