Bar-tailed or Black-tailed Godwits?

I have been to Stockton Sandspit a number of times and the vast majority of the  godwits are bar-tailed with maybe 5% black-tailed mixed in with them. Very hard to tell apart on the ground .... but in flight the black tails and wings of the BlackTails are easily seen. So your 40-50 birds are mostly  bar tails with maybe the odd black tail in there too.

If you see a flock of godwits in flight there, take a few pics and you will probably find a few black tails amongst the bar tails.