I agree with all of the above. When I was cutting in state forest lands up here we weren't allowed to use power equipment other than chain saw, truck and trailer. No dragging. I talked to a forester off the record, he agreed the reason was to not tear up the topsoil so the Dep of Forestry could replant without having to do a lot of dirt work. So I bucked mine where they fell and brought my truck as close in as I could for loading.
Around here it is a given any felled birch is going to be weight bearing at only a couple or three points and then sagging between those points. I marked up first. Chalk line where the base of the log straightened out, then marks at 16" down to the felling cut, and 16" marks up to the first major fork. I have I think blue, orange and yellow chalk in my saw box, one of those three is usually high vis on a felled tree.
Now is a good time to stop, have some hydration and look at the log to see where it is actually supported.
Next, if the base end is off the ground take those off 16" at a time as freebies, cut about 1/3 of the way through at the chalk marks up to the first fork, and then harvest the crown. I will take everything out of a birch crown down to about 3" in diameter, because I can zip open the bark while it is still attached to the tree and then lop off eyeballed 16" lengths. This is also a good time to make any needed rip cuts in forked pieces that would be impossible to split. While they are attached to the log you can do about anything to them. Just rip down the crotch of the split to the next chalk line, then cut two pieces off the limb, already halved, with one crosscut.
The last piece is to then look over the main log again to see where the stresses are in it and then cut it into shorter and shorter pieces, always on the chalk marks.
Peavey very handy. There were a few times I wanted a timber jack in the field, but a timber jack is a pain to use as a Peavey. I personally don't like a cant hook for round logs.
With spruces I mark the trunk while the tree is still standing. We were supposed to leave stumps less than 3" tall, so mark that cut, then 16" up, then another 16" up, usually 32" above the abandoned stump would be my felling cut with two rounds to cut off the stump before I was done. Once the tree is down mark the free trunk and cut the rounds off it, then limb a little, mark a little, buck a little, repeat until all you have left is a Charlie Brown Christmas tree at the top. You want as much wood off the log end as possible before cutting the limb supporting the free end. Once or twice in every tree the thing to do is cut the 16" round that has the supporting limb sticking out of it, and then limb the round on the ground, but most of the time I could limb and then buck my way up the tree.