I would like to be able to differentiate between seeing a bird and hearing a bird when I report. Perhaps adding the ability to H "species" and S "species."
Also, given the ability to add *exact* GPS coordinates (especially with the upcoming iPhone app), when you see a report that someone heard a bird vs. seeing one, you know that the birds might not be in such a geographically exact location. IMHO it adds to the richness of the sightings (although the term sightings looses its specificity) people are reporting.
I also don't see this implemented by other bird sighting websites, so this could be a nice way to initially differentiate Chiptracker.