I am reading B. Traven's adventure The Treasure of the Sierra Madre, which is about three men who secretly go prospecting for gold. On their way home with their new-found loot they cover their tracks by tearing down their mining camp. Howard (the most experienced of the party) verbally beams with pride over a job well done. Dobbs, another member, takes offense at Howard's response. The quoted section can be found here:
The mine was leveled to the satisfaction of Howard. Anybody now coming upon the mine by chance would never think that a mine had been worked here, or if at all, not during the last hundred years.
"Doesn't it give you guys a real joy to look at the place now?" Howard asked with pride in his voice.
"All right," Dobbs said, "you have it your way and you feel happy, so please, for the love of Mike's booze, leave us in peace with your feelings. Sometimes I think you must have been a preacher, only the hell of it is I can't figure out what church it was you wanted to catch birds for."
When I found a definition of bird (Definition 5.a) that is slang for fellow, I took Dobbs' words to catch birds for to be reminiscent of the Christian saying fisher of men, meaning the minister is actively looking for people to convert. In past conversations, Dobbs has been known to use slang like mug to refer to people. But being more familiar with the usages meaning a young woman or a person, especially one who is odd or remarkable, I thought this usage unlikely and continued to look for another.
So I wondered if Dobbs was making an allusion to bird dogs, who retrieve birds for their masters. (One might say a minister retrieves the lost for a higher power, a superior in the church or for God.) This could be an insult to Howard, the slight being that Howard would be a subordinate instead of the senior/equal he was when mining with Dobbs. This insult makes sense in this context, because Dobbs has a history of viewing Howard as a taskmaster, as shown by Dobbs's outburst when he cuts his own hand at the beginning of the chapter. But this analogy of bird dogs seems tenuous and elaborate.
I've searched Google for "catching birds," but the most relevant results are the proverb "A bird in the hand is worth two in the bush." I wondered if Dobbs was speaking of some duty, tradition, or superstition associated with ministers, but I have found nothing.
What does "to catch birds for" mean?