Ooh, that's interesting! I mentioned before the child on the 1881, and hadn't managed to pin down who he was - I have a possible birth ref, (a Joseph, I believe, without looking it up) but without ordering the certificate couldn't check it was the right one. I do indeed have the census on the tree, if you need to look it up.
If Mary Ann (Polly) was living with her father at the time of the 1881, do we know where Nathan snr was at that Census? I will have a look.
Hadn't thought to have a look at Familysearch, good one, Sluggie, worth a trawl through those, as the Corkes did mostly have their babies christened, even if they didn't much believe in marriage!