The New Zealand pigeon or kererū (Hemiphaga novaeseelandiae) is a bird endemic to New Zealand. Māori call it kererū in most of the country but kūkupa and kūkū in some parts of the North Island, particularly in Northland. Commonly called wood pigeon, they are distinct from the wood pigeon (Columba palumbus) of the Northern Hemisphere, which is a member of a different genus.
The New Zealand pigeon belongs to the family Columbidae, and the subfamily Treroninae, which is found throughout Southeast Asia,Malaya, Africa and New Zealand. The members of this subfamily feed largely on fruits, mainly drupes. New Zealand pigeons are members of the pigeon genus Hemiphaga (Bonaparte, 1854), which is endemic to the New Zealand archipelago and Norfolk Island. However recently a Hemiphaga bone was found on Raoul Island. The Chatham pigeon or Chatham Island pigeon (Hemiphaga chathamensis) is traditionally considered a subspecies of the kererū, but is here treated as a separate species.
The New Zealand pigeon is a large, 550–850 grams (19–30 oz), arboreal fruit-pigeon found in forests from Northland to Stewart Island/Rakiura, ranging in habitats from coastal to montane. The general morphology is that of a typical pigeon, in that it has a relatively small head, a straight soft-based bill and loosely attached feathers. It also displays typical pigeon behaviour, which includes drinking by suction, a wing-threat display, hitting with the wing when threatened, a diving display flight, a ‘bowing’ display, ritualised preening and ‘billing’ during courtship. New Zealand pigeons build flimsy, shallow, twiggy nests and feed crop milk to hatchlings.
The mainland New Zealand pigeon grows to some 51 centimetres (20 in) in length and 650 grams (23 oz) in weight, compared to 55 centimetres (22 in) and 800 grams (28 oz) for the Chatham Island variant. The head, throat and wings are generally a shiny green-purple colour, but with a bronze tinge to the feathers. The breast is typically white and the bill red with an orange-ish tip. The feet and eyes are red. Juveniles have a similar colouration but are generally paler with dull colours for the beak, eyes and feet and a shorter tail.
The New Zealand pigeons make occasional soft coo sounds (hence the onomatopoeic names), and their wings make a very distinctive “whooshing” sound as they fly. The bird’s flight is also very distinctive. Birds will often ascend slowly before making impressively steep parabolic dives; it is thought that this behaviour is often associated with nesting, or nest failure.
As generally accepted, there are three subspecies of New Zealand pigeon; of these, only two survive: H. n. novaseelandiae of mainland New Zealand and H. n. chathamensis of the Chatham Islands. The other subspecies, Norfolk pigeon (H. n. spadicea) of Norfolk Island, is now extinct. The subspecies differ in their plumage colour and physical morphology.
In 2001, it was proposed that H. n. chathamensis, the Chatham pigeon, was distinct enough to be raised to full species status, H. chathamensis, instead of the traditional subspecies status, H. n. chathamensis. Few authorities outside New Zealand have followed this, with most still considering it a subspecies.
The New Zealand pigeons are commonly regarded as frugivorous, primarily eating fruits from native trees. They play an important ecological role, as they are the only birds capable of eating the largest native fruits and drupes (those with smallest diameter greater than 1 cm), such as those of the taraire, and thus spreading the seeds intact. While fruit comprises the major part of their diets, the New Zealand pigeon also browses on leaves and buds, especially nitrogen rich foliage during breeding.
One of their favourite leaves to eat is from an introduced plant, the common plum tree. The diet changes seasonally as the availability of fruit changes, and leaves can comprise the major part of the diet at certain times of the year, such as when there is little fruit around.
Breeding generally depends on the availability of ripe fruit, which varies seasonally, annually (good years and bad years), and by location. New Zealand pigeons, like other frugivorous pigeons, feed on many species with tropical affinities, including the Lauraceae and Arecaceae which abound in the essentially subtropical forests of northern New Zealand. They also feed on podocarp species, thought to be relics of the flora of Gondwana, such as miro (Prumnopitys ferruginea) and kahikatea (Dacrycarpus dacrydioides). In the warmer northern half of the North Island, pigeons can nest all year round, except when moulting between March and May, provided enough fruit is available. Further south fewer subtropical tree species grow and in these areas breeding usually occurs between October (early spring) and April (late summer/early autumn), again depending on fruit availability.
New Zealand pigeons nest in trees, laying a single egg, in a flimsy nest constructed of a few twigs thrown together. The egg is incubated for 28–29 days and the young bird takes another 30–45 days to fledge. In seasons of plentiful fruit the pigeons can successfully nest up to four times.
Distribution and conservation
The introduced Australian common brushtail possum (Trichosurus vulpecula) and introduced species of rats — mainly the ship or black rat (Rattus rattus) but also the kiore or Polynesian rat (Rattus exulans) and brown rat (Rattus norvegicus) — have significantly reduced the amount of fruit available for pigeons and other native birds and also prey on eggs and nestlings.
Pigeon populations are also under threat from hunting, habitat degradation and poor reproductive success. Pigeons were very numerous until about the 1860s and large flocks used to congregate in fruiting trees to feed. Restrictions on the shooting of pigeons were enacted as early as 1864, with total protection since 1921, although the enforcement against hunting was not consistent. Some Māori protested, claiming a traditional right to hunt the pigeon.
The bird is protected under the Wildlife Act and there have been prosecutions for shooting it.