Wow, what rock have I been under? Google Book Search is too cool. The preview mode has a pretty good assortment of bird books including the Peterson Gulls of the Americas, Birder's Conservation Handbook, Birding in the America West, and many others. For many books, the previews are very detailed, but for many it is just one or two pages. Don't be fooled by the links that show a page number in the title. For many that is just the page that the preview starts on.