Hey Byron,
Thanks for the instructions, I know exactly where you mean. I was at Grass Lake a few times which is awesome for Cranes in the Spring and Summer.
As for which lens....tough question.
If you asked 20 people, you would get 20 answers. I suggest posting a question of which lens to buy in the Equiptment section on this forum.
One thing I have learned is when it comes to birds, you can never have a big enough lens. I only shoot birds. So I have a 500mm F4. I also have a 300mm F4 that I use for the odd bird that is nice enough to not fly away. I just bought a 200mm-400mm just in case the 300 is to far and the 500 is too close. Truth be told I'll probably trade them all in on the 800mm when Nikon releases it. A whole new world opens up when you get into the big glass. But it's a huge investment. I lucked out on all 3 of mine with some great deals from Nikon Canada.
Remember I only shoot birds, so those lenses work for me. If you are shooting anything else, people, places, bugs or flowers you should stick with something that is more versatile...and a heck of a lot cheaper...
There are lots of lenses out there. It is really a matter of what your budget is.
Like I said, post in the equiptment forum. You will get lots of feedback. People will give you good advice and suggestions. Then research online and check out reviews of each lens.
Once you have your choice narrowed down a bit, go to a camera store and play around. Rent one if you can for a weekend. Or borrow one from someone you know. People love to talk about there gear and some would even let you use their stuff for a few minutes if you meet themin the field. Even if you meet a Nikon shooter, ask to take a look, you will still be able to see the difference, and if you like then go look at the Canon equivalent.
Hope this helps a bit.
Feel free to ask me anything else.
Meghan