Prerequisites and Related Skills
Wilderness Survival
Hunting
Interrogation (Urban Environments)
You don't say whether these are prerequisits or related skills and how they interact with the Tracking Skill itself. This was a list, I believe, that was included in the stub as part of a suggestion... it needs to be expanded. Other things could be included... Lore of Animal Tracks, Lore of Local Geography, perhaps land navigation, etc. Animal behavior or whatever your tracking's behavior should be included on this list as well.
Also, you need to add a section on how someone learns tracking. It doesn't need to be very large, but indeed it should include how one learns to track - both singularly and with a teacher.
Novice:
A Novice has barely begun to track and does not do so very often.
Time spent doing tracking shouldn't factor in. Someone sees this and they might think.. wow I can't track very often at this level. Sure they can. They can track as much as they want.. they just aren't great at it.
Tracking humans and other such creatures is generally far out of their reach.
Why in the world? Humans are some of the easiest things to track in the woods. They aren't trying NOT go get eaten. They stumble and bumble around leaving footprints in soft soils and grabbing at branches breaking them.
Competent:
You mentioned spotting marks on trees twice - it sounds repetitive... And the human thing again... like I said.. humans are some of the easiest. I would remove this altogether. Otherwise, good work here.
Expert:
I wouldn't start out with who seeks them... I'd talk about their skill level instead and what they can do... an end message about how sought out they are might be nice though.
They enjoy being outdoors are it is like being in a different world to them.
Awkward.
An expert tracker is able to track their foes through grassland.
Trackers track all sorts of things... lost kids, prey, etc. I woudln't say foes here, I'd use a different word like targets.
They can pick up tracks through the movement of leaves, pine needles and hard packed ground.
Trackers should be able to do this at virtually every level, especially starting at competent. Duff - the debris under pine trees that comprise old needles and fallen twigs etc is extremely easy to leave tracks through and for a novice tracker to follow. Leaves are a bit more trickier but it depends on how old they are... really old ones its easy peasy to track through. New crunchy ones... a lot harder. So I'd add this at lower levels and change this sentence to read 'hard packed ground' only.
Master:
I like what you did for this.
I also think Eanos had some good suggestions.