Tom: As far as I know, the Koloa (as the pure Hawaiian Duck) has a population of around 2500. Most of these reside on Kauai (around 80%) in the Hanalei National Wildlife Refuge
. Most (if not all) of the Koloa here on Oahu or other islands are hybrids of the pure Koloa and Mallard. I see quite a few of them (hybrids...maybe pure), so I'll try and post some pictures.
I think they recently introduced Koloa back on Oahu and the Big Island.
As for re-introducing the Laysan Teal to their historical range...who knows. I think it might be difficult with the invasive (non-indigenous) predators that are located in those historical areas...which seemed to cause the rapid decrease in population years ago. But I'm with you...I hope they can someday.