Hi dhahn,
Some understanding of taxonmic lists is in order here. While Clements provides the currently accepted list of birds of the world, it does not agree in every aspect (common names, scientific names, species/subspecies, sorting, etc) with both ABA and AOU.
The difference can produce different counts for lifers from tax list to tax list.
If you bird outside NA, you will want Clements. If your ABA North American count is important to you, you will want the latest ABA tax list also.
This should get us started. Let me know if you have more questions.
Jeff |