I've been splitting a mix of oak, sassafras, and black birch, that I got recently from a relative, with more to go get. It was time to move it about 100ft, to it's long term sleep.
Nice! Welcome to the club! That black birch is some good stuff - I love that wintergreen smell. It dries pretty fast too considering it's right up there with oak on the BTU charts. However, birch bark is watertight; and if you leave any pieces unsplit, they will never really dry out and may actually rot. For those smaller diameter pieces that don't need to be split, you can "unzip" or score the bark with the chainsaw. Just make sure to use the lower part of the bar tip ("starting corner"), and not the upper part ("kickback corner"). This is much safer to do with whole branches though; after the pieces are cut to length it's hard to get them to stay put.
Nice score! All good wood!, the birch beats oak. I've got some burning now that I cut this summer. Got some rounds I hope are dry for when it gets real cold.
All birch is like that. If you don't split it once, right after cutting it, it's going to be punk shortly.