Stumbled across this on flipboard. I left the name of the character this theory centers around out of the title since would considering a spoiler - the masked bird man may be...
Detective Kevin Burris.
This idea originated on reddit so perhaps many of you are familiar with it (I think I might be the one person on voat who never used reddit). Good explanation here: http://www.sickchirpse.com/true-detective-season-2-conspiracy-theory
01. Burris is not 100% villain as he is attempting to break up an extortion ring that could ensnare a would be governor.
02. Burris was the one Velcoro was actually speaking to when he was waking up from a dream His father's words were Burris' words, and he was seeing a Conway Twitty impersonator on stage because that song was playing from the old radio.
03. Burris would have very easy access to both the ordinary nonlethal buckshot (at least when not aimed at a crotch, inducing heart attack). Bird man clearly did not want Velcoro dead. Even without lethal rounds, he could have just strangled him when he was unconscious.
Adding to that, I think the manner in which Caspere's body was readily displayed works with this idea - the ID was handy so people would know who he was, and it was a clear message to the other people engaging in blackmail (younger Chessani, Rick Springfield, etc) that their days of shaking down powerful orgy goers were over. Despite how gruesome Caspere's end was, it seemed pretty obvious from the start that this season was about shady practices and corruption, not serial murder.
Two possible flies in the ointment: Why kill Stan? Semyon pretty much says this for the audience. He is too minor in the scenes presented thus far to be much of a target. Unless more is explained on the topic, or some manner of flash back scene shows that he was in the know on the blackmail scheme, it doesn't fit. The other issue we don't really know what was going on with the torture shed at the end of episode five other than the fact that did appear to be about torture (bound to a chair, lots of blood, not an immediate death). That could open up a curve ball that debunks all of this. But the volume of carrion birds was very on the nose, so I don't doubt that the bird man carried out that bloodshed. It also slightly odd that somebody as "in the loop" on the investigation would wait until his own detective was close to the weekend at bernie's car to torch it, but then again, that could have been a second masked men sent to complete a task.