What is a "slash combo"?
eBird's taxonomy has many non-species taxa including what we call "Slash Combos". These are meant to be used when you've narrowed down the identification to two species, but you're not sure which one it is. For example, distant grebes can be difficult. It's easy enough to tell if they are Western/Clark's Grebes, but it's really hard to tell exactly which species it is. In this case, use the "Western/Clark's Grebe" slash combo to enter your data.