Birch is a pretty good wood for spars. Caveat: in ship model books and magazines stories about warped birch dowels have been floating around for a long time. In more than fifty years, and probably hundreds of dowel's I've bought, I've never seen one warp - and I've never met anybody who has.
I think the problem originated with birch dowels that were cut across the grain of the wood. Apparently the dealers have stopped doing that. If those drumsticks are straight now, they aren't going to warp.