I enjoy pretty much everything outdoors. The hobbies I have pursued seriously include:
Cliff Jumping (if that counts)
There are probably more that I'm forgetting. I enjoy tracking, foraging for wild edibles, general wildlife observation and identification, botany, etc. I'm guessing you wouldn't count more "proper" outdoor sports like tennis? I would say that to be counted as a hobby it should be something one is proficient at and enjoys doing. This could perhaps rule out windsurfing for me as it is a fairly new pursuit and I'm certainly not an expert at it yet. The other listed activities I consider myself very competent at.