Don't know that we offered anything of any real use
Looking again it reminded me of the colour and varying opacity/translucence of Blue Pearline from George Davidson (and other factories which produced similar) - although this bird is no doubt second half C20 in date.
Apparently the colour in Blue Pearline was provided by cobalt (uranium in the yellow version), but the mix also contained phosphate of lime (instead of powdered calcined animal bones??), arsenic and limespar, without which the extremities wouldn't develop into that milky opaque shade when re-heated.
If you hold pearline up to the light, there is a degree of 'sunset glow' but this appears only in the immediate vicinity of the re-heated opaque areas.
Does this bird show any sunset glow?
It's unlikely that this piece contains any arsenic, and it might well be that the pedestal and bird have been produced separately in order to create the different shades, and then fused together as a final process. It might well be from the Gulf of Venice - they seem to have a passion for making ducks, swans etc.
coming back to Sue's comments..........the only book I have on milk glass is Belnap - which is now very dated - great if you simply want pictures of milk/slag glass patterns/designs, but unfortunately Belnap contributes nothing regarding the make up of milk glass - although it may well have been opacified by tin oxide rather than cryolite as in vitro porcelain.
Belnap comments in his book that to qualify as milk glass, one of the original criteria was that the colour had to be white, but probably other colours now accepted - however, it does seem that a uniform opaqueness was essential.
Sorry this is rambling.
None of which helps with attribution for this piece, but nice if you collect blue birds