What is the "Add a species" box used for?
If you can't find the species you're looking for on either the "Most probable" or "Rare species" versions of the checklist you can then use the "Add a species" window to search for a new species for the checklist. Type in the species common name and click "Find it." You will then see a drop-down list of possible results. Choose the species from the resulting list and then click "Add to list" to add it to your checklist. If you have trouble finding the species you're looking for try to be less specific by searching something like "Flycatcher". You'll then see all the flycatchers in our taxonomy and you can choose the species of interest.