The Southern Bell Frog, Litoria raniformis, was introduced to New Zealand in the late 1860s from Tasmania by the Canterbury Acclimisation Society. They have been very successful in New Zealand and can now be found throughout most of the country.
These frogs are the largest frogs to be found in New Zealand with females reaching over 100mm. They are similarly coloured to the Green and Golden Bell Frog (found only North of Gisborne) but often have a warty back. They generally have more dark brown or black blotches on the back and there is always a pale green stripe down the middle of their back (although this can change in intensity depending upon environmental conditions). The back of their thighs and groin area are bright blue to turquoise and the belly looks granular. The fingers lack webbing while the toes are almost completely webbed. There are no suckers on the ends of their toes or fingers.
The call is similar to the Green and Golden Bell frog but is not as drawn out. It can be best described as crawcrocrocrocrok (in Australia it is also known as the Growling Grass Frog). Males usually call while floating in water.
They seem generally to prefer to breed in permanent lakes, swamps and dams with still water.
It's a few hundred metres to the nearest water from The Cottage but I assume that's a mere hop or two for them. I wondered for a few seconds why he was climbing up my door - he was up on the glass when I first saw him/her - though as s/he has no suckers I'm not sure how s/he managed that. Obviously it was the large amount of insects gathered on the glass attracted by the house lights that in turn attracted the frog.