Originally posted by Mharr:

That's interesting, what's the harpoon advantage? Just quicker to fire, or does it have a wider hitbox?

The advantage is infinite ammo. You can keep throwing it over and over at birds without wasting the arrows you are trying to make/save for the boss fight. It also handles better than a spear for throwing (it returns to your hand right away without having to be picked up).

To add to this conversation, I have over 400 hours in valheim and I've never seen a tree drop a feather. I've always just hunted birds to get them. There are sometimes some in chests, but not many.