The Cute Tiny Tomtits With Oversized Heads On A Ball Of Yellow Feathers

The tomtit (Petroica macrocephala) is a small passerine bird in the family Petroicidae, the Australasian 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 Māori and English names. There are several subspecies 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 Foster's rule or the island effect. Birds from the main islands weigh around 11g, compared with birds from Snares Island, which weigh in at 20 g.