That's also unclear to me, Chestnut Antpitta is only in Peru (and I suspect one of the 16 species is the undescribed, vocally distinct 'Chestnut' Antpitta population in Pasco, Peru), so the six species from Colombia mentioned in the twitter post could be the five mapped by Andres Cuervo plus Bicolored, the only problem is that none of the six specimens pictured in the twitter post look like Bicolored
I had a total brainfart. I am well aware of the Rufous / Chestnut affinities, but when I thought about 6 for Colombia I thought about Tawny instead of Chestnut so included one for that. Oops! So 6 for Colombia would then presumably be the 5 forms of Rufula + Bicolored.
I also assume Chestnut will be a two-way split. What is interesting to me is the lack of vocal distinction between W Andean birds and C Andean birds - assuming birds at, say, La Eme, must be the W Andean form? To my ear the sound well within the scope of nominate G rufula rufula from the Cen Andes to S Ecuador. But then again the forms in S Peru/Bolivia are vocally fairly similar to each other as well.
I am curious what the 16 species would be. Typically we hear about a roughly 9-10 way split of G rufula:
Santa Marta
Perijá
Bogota/E Andes/Chingaza/various name for this form I've heard
W Andes
nominate (C Colombia - S Ecuador)
Cajamarca (N Peru)
obscura (Cen Peru - not aware of a name name for this taxon)
occabambae (Cusco region - again not aware of names for this)
cochabambae (at least near Cochabamba, Bolivia)
and perhaps another taxon in N Bolivia?
That leaves 6 slots open...
-Bicolored Antpitta
-N Chestnut Antpitta
-S Chestnut Antpitta
-perhaps Gray-naped Antpitta is considered part of this complex as well?
That would still leave 1-2 unexplained... perhaps a N/S split of Bicolored Antpitta?