I did some 'quality' surfing of the net (rather than Asking Jeeves) and it seems:
1. All birds need salt in the same way we do.
I'm going to guess that the rough quantity they need is in relative proportion to us. So if the human recommendation is about 1.6g (UK) then the implied recommendation for birdy is 0.008g (8mg) salt.
2. Some wild species need "salt licks" in order to digest the type of food they eat. They don't eat that sort of food in the UK so presumably they don't need the 'salt lick'....however no doubt they are getting more than just the digestive effect of the salt lick....that means its slightly more complex for some breeds (amazons, macaws..)
3. Salt doesn't just mean table salt...I presume the Grey supplements are a Calcium salt of some sort. That side of things is too complimicated so I'll stick to table salt:
If birdy is looking for 8mg of salt a day maximum (all figures approximate):
I've adjusted the values below for a single 'chunk' or nut, the sort of thing you would give your bird as a snack or treat:
Any salted food (a crisp, a nut) ..................20mg or more (3x daily urgh) (I think we knew this!)
A little chunk of dry toast......................20mg (if they ate the whole piece)
Spoon of unsalted sunflower seeds...........1mg or less (I think this shows the background level of salt in bird seed is very low)
Apple...............................................near zero (fruit and veg are all like this)
Apple Juice (bought not squeezed)............just under 1mg (one to watch on the packaging)
Chunk of pizza...................................40mg (all ready made commercial food is VERY bad)
The main thing is we all know most of the above treat goes on the floor so it's not that bad, it's only the actual salt covered food that's bad.
I think I'm happy with my routines here but I'll aim for unsalted butter, low sodium bread etc and avoid the urge to let them have pizza crust etc
Unhelpfully they would bite off my arm for a salted crisp....
[lthough the above makes sense I'd be very happy for anyone actually qualified to correct it if necessary!!]