Handheld Birds

Five or six months ago I bought the 5th edition of National Geographic's Field Guide to the Birds of North America. I very much like the layout and the clarity of drawings, as compared to photographs. (I still use Kaufman's field guide most of the time since it is more compact and just "works" for me. I use Geographic's guide as a backup source.)
Even before getting the Geographic I was intrigued by their birding software for Palm based PDAs. My Palm 700p Treo is always with me and pretty much runs my life as well as handles all of my phone calls & voice mail. However, the cost prevented me from getting the software -- initially, I think it was about $250 for just the software card.
The price then went down to $199, but I still resisted -- until their latest temporary (?) reduction to $99. I've had the card installed on my Treo for about a month and I use it more than Kaufman.
It contains more information than the printed version, and -- the main selling point for me, other than portability, is the fact that it has recordings of bird songs and calls. If nothing else, it's a great tool for learning them -- a weak spot in my birding skills.
The software also allows you to maintain bird lists for each outing and upload them to eBird. Another neat feature is the ability to identify the strange bird you're looking at from among the 867 North American birds by entering factors such as the month of the year, state, size, colors, etc. Paging through a field guide can be bewildering for the beginner -- this software quickly narrows the search down to a reasonable number.
Take a look at Geographic's Handheld Birds web site for more information. You may also want to explore the tutorial.
Highly recommended, particularly if you already own a Palm!