tio's Identifications

Is there a bird vet in the house ??
A fat Silver eye with what looks like a prolapsed rectum gorging it's self on Coprosma berries.
It had a 2nd bird with it that was grooming around it's neck area ... ??
Thoughts those of you with some knowledge.
ID spot not acurate

There's possibly four of these Arctic migrant birds in NZ at present.
Possibly two are at Lake Ellesmere.
It blows my mind as to how such a small bird has the body resources to make such a long flight.
The Little Stint that is even smaller is with this group of waders it's smaller again.
Think Sparrow sized flying from Siberia.
Very Cool