I've got eight birds-mouth staves that don't fit together properly in two ways: All eight staves do not fit snugly and there are two significant gaps between staves along the taper.
My guess is the saw blade was not set precisely at 45*. Practice pieces(one set of eight at 24" and one set of eight at 36") appeared to be cut correctly as they fit tightly with no gaps along their lengths. As for the gaps, my guess is that the staves were not tapered uniformly - a result of the tapering technique I used (power-planing two staves at a time followed up with a hand plane).
Other factors contributed to what happened here: Using different table saws for different cuts, using new-to-me techniques (tapering and cutting the V-notch on the table saw). Frankly, I found setting up the table saw to cut the V-notch to be more fiddly and more difficult than setting up the router table & jig to cut the notches on previous spars.
I have enough material to make two more staves. So, one option is to make the two staves and see if that helps at all. If that doesn't work, then a second option is to purchase additional material for a new mast. If creating a new mast, I will probably revert to using the router table to cut the notches and I will use the shooting-board-on-the-table-saw technique (described last week for me by Chris Ring) to cut the taper. Do I have any other options?