Barnes and Noble has a fantastic deal on The Bird Songs Bible, which features all 747 breeding birds in N. America and their SONGS. It was originally issued for $125 (the book/player weigh at least 10 pounds) - and I found it locally at BN on clearance for $25 - with the educator discount, only $20. They also have it on clearance at BN.com: http://www.barnesandnoble.com/w/bird-songs-bible-les-beletsky/1103746910?ean=9780594232056
My boys absolutely LOVE paging through the beautiful illustrations, and I used it the other morning to double check a robin's call after I came back from my morning walk. (They're poky when it comes to getting back to AK.)
It's quite the tome, but definitely worth it, IMO.