A friend of mine showed me this series on DVD. I was so impressed I couldn't wait to purchase the Blu-Ray version and watch it at 1080p resolution. It turns out that not every scene is filmed in high definition, which is understandable given the conditions of some of the filming. What REALLY disappointed me about this version, however, is that much of the content is missing! The DVD version has a short documentary piece after each section that shows how the filming was done. This is actually some of the most interesting content. It's incredible, for example, how many days a photographer spent hiding in a blind to film a rare bird in the Amazon. When I got the Blu-Ray set I searched and searched but all this "making of" content is not included!