Yellowhead or yellowhammer

[lucindigo]

I realize this is usually resolved by location and by the fact that mohua/yellowheads are very rare. However, I can't stop going back and forth in my head about which it was, so any help would be appreciated! A couple days ago, at Purakaunui Bay in the Catlins, I saw two bright yellow birds fly into some bushes near the beach. I noted at the time that they had dark/almost green backs and I didn't notice any brown on the front. The bushes were close to some farmland, but the location is still fairly close to the Catlins River where mohua are known to be sighted.

Thoughts?
Thanks in advance!