The kākāriki karaka began nesting en-masse for the season in September. Then second nests in November. Then perhaps a third nest in January/February. Then perhaps birds who fledged in November may be ready for their first nest sometime in autumn (they may breed within 3-4 months of fledging).
We (OFP volunteers) worked out that the easiest way to find a nest is to watch a previously-used nest hole. There is a good chance the pair who used it last season will use it again this season. Pairs commonly have about three nest holes in circulation. They may start with nest 1, move onto 2, then onto 3, then go back to 1 for their fourth nest.
If a pair don't reuse a nest hole there is a decent chance some other pair will. They may have confidence it's a suitable site (they'll see signs of previous use) and make themselves at home.
Anyway, here's a favourite photo of mine from a nest watch. This is an unbanded pair using a previously used nest hole. The male had called the female off for a feed, here they are overhead courtship feeding. This photo was taken a long way overhead, at midday on a bright sunny day. The birds are in deep shade, and the blue reflects chromatic aberration in a cheap lens. I still like it. 😊

A nest was discovered today. A keen volunteer, James Davies, had finished the ranger course at the Nelson Polytechnic. He was keen on kākāriki karaka, and spent some time with us (Brook kākāriki volunteers). Today we were trying to find new nests (or second nests). James instinctively followed a bird 200m away from where he was watching, and waited. I caught up with him while he was having lunch, and almost immediately heard the sound of nestlings downhill. James went on to another nest watch and I moved downhill to where I'd heard the sound and waited. An hour later I heard the nestlings again, this time uphill! I moved back up, next time (an hour later) I heard them they were off to the side, and I quickly sighted a male feeding nestlings at the nest entrance. I went straight for video, and got a 30 second hand-held clip. It rained for the next few days, three days later I went back up with my tripod intending to film them properly but the nest was empty (the fledglings were in the canopy). If James had not followed his instincts we'd not have found this nest. A team effort. James was subsequently employed by the Department of Conservation on the Kākāriki Karaka Recovery Programme.