If you are at the level of 'Forum Index' or 'Birds of Hong Kong', by holding the cursor over the group of birds, you can see a full list of species contained in that group. The current arrangement is not ideal, but at least doing this speeds up the process of seeing what is inside each group.
Given the current layout of the Forum, it is difficult to see how to change it without creating unwieldy titles for each section. Species numbers from The Avifauna might be one way, but that presupposes people have some broad idea of what these are. A link to the list could be provided, but that would add time to a search for a particular species, probably more than would occur by holding the cursor over different groups.
However, jacanas being inside the 'rails' group is not this kind of issue. Jacanas are shorebirds.
Geoff
