The tomtit (Petroica macrocephala) is a small passerine bird in the family Petroicidae, the Australian robins. It is endemic to the islands of New Zealand, ranging across the main islands as well as several of the outlying islands. It has several other English names as well. There are several sub-species showing considerable variation in plumage and size. The species is not threatened and has adapted to the changes made to New Zealand’s biodiversity.
The tomtit is a small (13 cm, 11 g) bird with a large head and a short bill. The male North Island subspecies has black head, back, wings (with a white wing bar) and a white belly. The subspecies from South Island, the Chatham Islands and Auckland Islands are similar but have a yellow band across the breast between the black head and white belly. The females are brown instead of black. The Snares Island subspecies is entirely black, and is known as the black tit.
The island subspecies of tomtits show a striking variation in body size, being considerably larger than their mainland relatives, a tendency known as the island rule. Birds from the main islands weigh around 11g, but birds from Snares Island weigh in at 20 g. source