I’ve stumbled upon this thread and decided to revive it.
You should answer the open challenge before reviving it with your own challenges really
But in any case:
1) Night Parrot
2)
3) I suspect you mean Congo Peafowl, although it wasn't found living until 1955 and was merely *described* in 1936 from taxidermy remains which James P. Chapin discovered in a Belgian museum two years earlier.
4)
5) Dusky Seaside Sparrow
6) Painted Vulture (though I'd use the term unproven rather than theoretical, which implies it was always nothing more than a thought experiment)
7) Caribbean Flamingo
8) Nicobar Pigeon
9) Kaua'i 'O'o - although your description could also cover Heath Hen and a few others
10) Galapagos Penguin