re: What do you attribute the migration change to?

I majored in wildlife in college, so I'm always studying up on interesting topics. That is not one I've delved into as deeply as others, but maybe in my spare time I will do alittle more reading. I have some texts that may shed some light on the subject if I dust them off.

That is an interesting number, but with the advances in farming technology, I have a hard time believing the amount left would be more than it was before, although there may be more available since they are not tilling it under. Essentially, less waste on the ground, but none of it is plowed under, making it all available.

Now, there are some harvest practices that purposely leave grain for wildlife. I could definitely see that being a factor as well.