That probably depends on what you mean by "Nightbird I". There is a model called the Nightbird I which is sort of a stripped down spruce top no binding rosewood fretboard version, and then there is the "first edition" Nightbird which came in many incarnations and finishes but is pretty much a top-tier instrument all around.
The Nightbirds are all chambered except for the ST and DX (which probably should have not been called Nightbirds) and the ones with maple tops (like the IIs) are probably heavier than the spruce ones, but I'm not sure that's a reliable thing to claim.
I'm in the process of moving all of them back into the house so I'll get to weigh them all.
