eBird users are probably aware of the Top 100 feature where you can select state 
or county then either year or all time. I'm curious if anyone has an easy way to 
figure out from your all time list which species are missing. It shows you the 
total species for the year or all time but wouldn't it be nice to be able to 
quickly display which ones you are missing? e.g., my St. Mary's eBird list 
(which isn't my complete St. Mary's list) is 268 while the cummulative list is 
319. If I could figure out a quick way to sort out the missing species, I'd put 
some extra effort into digging out those species or certainly chase them if 
reported ;)
 
Tyler Bell

California, Maryland