[Lesser or Greater Scaup? Or something else?]

I like lesser for both, especially the second, but real pics would be nice

[Help ID]

Its definitely a house finch. 

[rtha]

Agreed

 

[Black and white bird inJoshua Tree National Park]

Definitely. You can tell by the placement of the white at the end of those long, black wings.

[What bird is this (Kauai)]

Bump

[Mystery Bird from Colombia (Caldas Province)]

It looks like a seedeater of some kind... Not sure though