Extralimitals

To me, the rainbow bee-eater is a species that is confounding in the way that, despite being an annual summer migrant to southeast Australia, there has not been even one record of the species in New Zealand.

Because of that, this species could be called an 'extralimital' species for New Zealand.

Extralimital species are birds that are considered likely to eventually occur in a particular area, but have never been recorded there in the past. Some field guides include extralimital species for the areas that they cover, but to my knowledge, there has yet to be a NZ field guide to include them. Given the fact that the New Zealand region is made up of fairly isolated islands, however, I consider this to be sensible.

My opinion on extralimital birds is that, unless an extralimital bird regularly occurs literally only a few tens of kilometres away from a region that it seems it could eventually reach, it shouldn't be included in a field guide for that region.

Yes, there have been species that have occurred in an area a very short time after being featured as an extralimital in a field guide for that area, but that doesn't mean that including extralimital species in serious bird guides should be encouraged.