My attitude is, why spend all that money on camera gear if you're too afraid to use it on the most important subjects?
Forget carrying a camera bag, forget carrying extra lenses and tons of extra gear. Pare it down to the minimum: camera body with walkaround lens, enough media cards to take one days pics (for me that's one in camera and one spare), a pocket-size tripod, and my infrared remote. I also add my Canon Speedlite 220EX.
My camera rides on a long shoulder strap, where I can get to it whenever I need to shoot a picture. Why keep it in a bag when you're walking around the biggest photo opportunity in the world?
My spare media card, flash, and remote fit into my pockets comfortably. Others use a small waist pack. Why carry a huge bag full of stuff you won't need?
I have a great walkaround lens - my Sigma 18-125 - that gives me wide enough wide angles and long enough zooms. Why carry 3 heavy, expensive lenses around when one will do? Besides, picture opportunities come and go mighty fast - changing lenses can cause you to miss them.
I don't even turn my camera off. I have it set up to go into sleep mode to save battery power, but coming back from sleep mode takes less time than starting up from the Off position, so I have more chance of catching those quick pictures.
Don't be afraid to take the good cameras into the parks. The better the camera you have with you, the more chance you will have of getting those good pictures.
Here are my favorites from my last trip, taken with with my Digital Rebel and the 18-55 kit lens:
[click any pic for full-size version]












